JP5315993B2 - Polarizing plate protective film, polarizing plate, liquid crystal display device - Google Patents

Abstract

A polarizing plate protective film forming a polarizing plate by sandwiching a polarizer with two of the polarizing plate protective films, wherein at least one of the two polarizing plate protective films exhibits Ro defined by Expression (I) of 0 to 10 mm and Rt defined by Expression (II) of -20 to 20 mm, and also at least one of the polarizing plate protective films has a hard coat layer: Expression (I): Ro=(nx-ny)xd; Expression (II): Rt={(nx+ny)/2-nz}xd; wherein nx is a refractive index in a delayed phase axis direction in a plane of the polarizing plate protective film, ny is a refractive index in a direction at right angles to the delayed phase axis in the plane, nz is a refractive index in a film thickness direction, and d is a film thickness (nm).

Description

  The present invention relates to a polarizing plate protective film, a polarizing plate, and a liquid crystal display device. More specifically, the retardation value fluctuation is small, and the polarizing plate protection has excellent stability against polarizer deterioration, polarizing plate dimensions, and polarizing plate curl. Related to film.

  Along with high performance and high quality of liquid crystal display devices, as a polarizing plate protective film used for polarizing plates, the long-term storage stability of polarizers under high temperature and high humidity, dimensional stability of polarizing plates, and curling characteristics of polarizing plates However, there is a need for a polarizing plate protective film that can withstand severe environmental fluctuations.

  In particular, a polarizing plate adjacent to a backlight is required to have long-term durability with heat from the backlight. Recently, in order to increase the light efficiency of the backlight, a liquid crystal display device has been designed to place a brightness enhancement film at a position sandwiched between the backlight and the liquid crystal cell. The light is often polarized, and the polarizing plate protective film is required to have an optical design of the film that does not exhibit birefringence due to the heat of the backlight.

  Currently, as a polarizing plate protective film of a liquid crystal display device, a film made of cellulose ester is used. Cellulose ester films are generally formed by solution casting from the standpoint of ensuring flatness, etc., and the film expands in the film thickness direction as the solvent evaporates, and the film thickness increases with respect to the refractive index within the film plane. The refractive index in the direction is low. As a result of taking into account the display mode of the liquid crystal display device, other retardation films, and the phase difference of the members, an optimal polarizer protective film for securing the viewing angle of the liquid crystal display device is obtained in the thickness direction and the in-plane direction. There has been a demand for a film having the same refractive index, and further a polarizing plate protective film having a higher in-plane refractive index.

Patent Document 1 discloses that by adding an ethylenic polymer, a film with little deterioration of a polarizer under high temperature and high humidity and with little retardation in the thickness direction can be obtained. However, it has been found that the durability level of a polarizer under high temperature and high humidity that is currently required cannot be achieved by simply adding an ethylenic polymer. In addition, it has been found that the more the ethylenic polymer is introduced, the more the deterioration of the polarizer becomes worse in order to reduce the retardation.
JP 2003-12859 A

  An object of the present invention is to provide a polarizing plate protective film that has little retardation value fluctuation and has excellent stability against polarizer deterioration, polarizing plate dimensions, and polarizing plate curl.

The above object of the present invention is achieved by the following configurations.
(1) In two polarizing plate protective films sandwiching a polarizer for forming a polarizing plate, at least one of the two polarizing plate protective films has an Ro defined by the following formula (I) of 0 An ethylenically unsaturated monomer Xa having ˜10 nm, Rt defined by the following formula (II) of −20 to 20 nm, a hard coat layer, and at least no aromatic ring and no hydrophilic group in the molecule; A polymer X having a weight average molecular weight of 5,000 to 30,000 obtained by copolymerization with an ethylenically unsaturated monomer Xb having no hydrophilic ring in the molecule and having a hydrophilic group, and an ethylenically unsaturated group having no aromatic ring. Cellulose containing a polymer Y having a weight average molecular weight of 500 or more and 3000 or less obtained by polymerizing a saturated monomer Ya, or a polyester represented by the following general formula (3) or (4) Polarizing plate protective film, which is a ester film.
Formula (I) Ro = (nx−ny) × d
Formula (II) Rt = {(nx + ny) / 2−nz} × d
(Here, the refractive index in the slow axis direction in the plane of the polarizing plate protective film is nx, the refractive index in the direction perpendicular to the slow axis in the plane is ny, and the refractive index in the thickness direction of the film is nz, d. Represents the thickness (nm) of the film.)
Formula _{(3) B 1 - (G} -A-) wG-B 1
(In the formula, B ₁ represents a monocarboxylic acid, G represents a divalent alcohol, A represents a dibasic acid, and B ₁ , G, and A do not contain an aromatic ring. W represents the number of repetitions. A plurality of B ₁ and G may be the same or different.)
Formula _{(4) B 2 - (A} -G-) zA-B 2
(In the formula, B ₂ represents a monoalcohol, G represents a divalent alcohol, and A represents a dibasic acid.
The B ₂ , G and A do not contain an aromatic ring. z represents the number of repetitions. A plurality of B ₂ and G may be the same or different. )
(2) The polarizing plate protective film according to (1), wherein the polymer X is represented by the following general formula (1), and the polymer Y is represented by the following general formula (2).

General formula (1)
_{- [CH 2 -C (-R 1} ) (- CO 2 R 2)] m- [CH 2 -C (-R 3) (- CO 2 R 4 -OH) -] n- [Xc] p-
General formula (2)
_{Ry- [CH 2 -C (-R 5} ) (- CO 2 R 6 -OH) -] k- [Yb] q-
(In the formula, R ₁ , R ₃ and R ₅ represent H or CH _3. R ₂ represents an alkyl group having 1 to 12 carbon atoms and a cycloalkyl group. R ₄ and R ₆ represent —CH ₂ —, —C ₂ H ₄ — or —C ₃ H ₆ — is represented.
Ry represents OH, H or an alkyl group having 3 or less carbon atoms. Xc represents a monomer unit that can be polymerized to Xa and Xb. Yb represents a monomer unit copolymerizable with Ya. m, n, k, p, and q represent a molar composition ratio. However, m ≠ 0, n ≠ 0, k ≠ 0, m + n + p = 100, and k + q = 100. )
(5) The polarizing plate protective film having the hard coat layer is a cellulose ester film containing at least the polymer X and a polyester represented by the following general formula (3) or (4) (4 The polarizing plate protective film of description.

(3) When the said cellulose-ester film contains the polymer X and the polymer Y, the content is the range which satisfies following formula (i) and Formula (ii), (1) or ( The polarizing plate protective film as described in 2).
Formula (i) 5 ≦ Xg + Yg ≦ 35 (mass%)
Formula (ii) 0.05 ≦ Yg / (Xg + Yg) ≦ 0.4
(In the formula, Xg represents the content (mass%) of polymer X relative to the cellulose ester, and Yg represents the content (mass%) of polymer Y relative to the cellulose ester.)
(4) The polarizing plate protective film according to any one of (1) to (3 ), wherein the hard coat layer has a thickness of 1 to 30 μm.
(5) A polarizing plate, wherein the polarizing plate protective film according to (4) is bonded to at least one surface of a polarizer.
(6) A liquid crystal display device using the polarizing plate according to (5) .

  According to the present invention, there were obtained a polarizing plate protective film, a polarizing plate and a liquid crystal display device having little retardation value fluctuation and having excellent stability against polarizer deterioration, polarizing plate dimensions and polarizing plate curl.

  The best mode for carrying out the present invention will be described in detail below, but the present invention is not limited thereto.

  The polarizing plate protective film of the present invention has a retardation value Ro of 0 to 10 nm, Rt of -20 to 20 nm, and a hard coat layer.

As a method of adjusting the Ro and Rt of the invention, the cellulose ester film of the present invention are aromatic view of transparency, an aromatic ring and a hydrophilic group having no ethylenically unsaturated monomer Xa and the molecule in the molecule A polymer X having a weight average molecular weight of 5,000 to 30,000 obtained by copolymerizing an ethylenically unsaturated monomer Xb having no ring and a hydrophilic group, and an ethylenically unsaturated monomer Ya having no aromatic ring It contains either a polymer Y having a weight average molecular weight of 500 or more and 3000 or less obtained by polymerization, or a polyester represented by the following general formula (3) or (4).

<Polymer X, Polymer Y>
In general, a substance having an aromatic ring in the main chain in a monomer is known to have positive birefringence as well as birefringence of cellulose ester, and does not cancel the retardation value Rt of the cellulose ester film. It is preferable to add a material having negative birefringence into the film.

  The polymer X of the present invention is a copolymer of an ethylenically unsaturated monomer Xa having no aromatic ring and a hydrophilic group in the molecule and an ethylenically unsaturated monomer Xb having no aromatic ring and having a hydrophilic group in the molecule. It is a polymer having a weight average molecular weight of 5,000 to 30,000, and is preferably a polymer represented by the following general formula (1).

General formula (1)
_{- [CH 2 -C (-R 1} ) (- CO 2 R 2)] m- [CH 2 -C (-R 3) (- CO 2 R 4 -OH) -] n- [Xc] p-
(In the formula, R ₁ and R ₃ represent H or CH _3. R ₂ represents an alkyl group having 1 to 12 carbon atoms or a cycloalkyl group. R ₄ represents —CH ₂ —, —C ₂ H ₄ —. Or -C ₃ H _6- , Ry represents OH, H or an alkyl group having 3 or less carbon atoms, Xc represents a monomer unit polymerizable to Xa and Xb, and m, n and p are molar compositions. (Where m ≠ 0, n ≠ 0, m + n + p = 100).
Although the monomer as a monomer unit which comprises the polymer X of this invention is mentioned below, it is not limited to this.

  In X, the hydrophilic group means a group having a hydroxyl group or an ethylene oxide chain.

  Examples of the ethylenically unsaturated monomer Xa having no aromatic ring and no hydrophilic group in the molecule include methyl acrylate, ethyl acrylate, propyl acrylate (i-, n-), and butyl acrylate (n-, i- , S-, t-), pentyl acrylate (n-, i-, s-), hexyl acrylate (n-, i-), heptyl acrylate (n-, i-), octyl acrylate (n- I-), nonyl acrylate (n-, i-), myristyl acrylate (n-, i-), acrylic acid (2-ethylhexyl), acrylic acid (ε-caprolactone), acrylic acid (2-hydroxyethyl) ), Acrylic acid (2-ethoxyethyl), or the like, or those obtained by replacing the acrylic ester with a methacrylic ester. Among these, methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, and propyl methacrylate (i-, n-) are preferable.

  The ethylenically unsaturated monomer Xb having no aromatic ring in the molecule and having a hydrophilic group is preferably acrylic acid or methacrylic acid ester as a monomer unit having a hydroxyl group. For example, acrylic acid (2-hydroxyethyl), List acrylic acid (2-hydroxypropyl), acrylic acid (3-hydroxypropyl), acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl), or those in which these acrylic acids are replaced by methacrylic acid. Preferred are acrylic acid (2-hydroxyethyl) and methacrylic acid (2-hydroxyethyl), acrylic acid (2-hydroxypropyl), and acrylic acid (3-hydroxypropyl).

  Xc is not particularly limited as long as it is an ethylenically unsaturated monomer other than Xa and Xb and copolymerizable, but preferably has no aromatic ring.

  The molar composition ratio m: n of Xa and Xb is preferably in the range of 99: 1 to 65:35, more preferably in the range of 95: 5 to 75:25. The molar composition ratio of Xc is 0-10. Xc may be a plurality of monomer units.

  When the molar composition ratio of Xa is large, the compatibility with the cellulose ester is improved, but the retardation value Rt in the film thickness direction is increased. When the molar composition ratio of Xb is large, the compatibility is deteriorated, but the effect of reducing Rt is high. Further, if the molar composition ratio of Xb exceeds the above range, haze tends to occur during film formation, and it is preferable to optimize these and determine the molar composition ratio of Xa and Xb.

  In order to synthesize such a polymer, it is difficult to control the molecular weight in normal polymerization, and it is desirable to use a method that can align the molecular weight as much as possible by a method that does not increase the molecular weight so much. Such polymerization methods include a method using a peroxide polymerization initiator such as cumene peroxide and t-butyl hydroperoxide, a method using a polymerization initiator in a larger amount than normal polymerization, and a mercapto compound in addition to the polymerization initiator. And a method of using a chain transfer agent such as carbon tetrachloride, a method of using a polymerization terminator such as benzoquinone and dinitrobenzene in addition to the polymerization initiator, and further, Japanese Patent Application Laid-Open No. 2000-128911 or 2000-344823. Examples thereof include a compound having one thiol group and a secondary hydroxyl group, or a bulk polymerization method using a polymerization catalyst in which the compound and an organometallic compound are used in combination. Although used, the method described in the publication is particularly preferable.

  The hydroxyl value of the polymer X is preferably 30 to 150 [mg KOH / g].

(Measurement method of hydroxyl value)
This measurement conforms to JIS K 0070 (1992). This hydroxyl value is defined as the number of mg of potassium hydroxide required to neutralize acetic acid bonded to a hydroxyl group when 1 g of a sample is acetylated. Specifically, sample Xg (about 1 g) is precisely weighed in a flask, and 20 ml of an acetylating reagent (a solution obtained by adding pyridine to 20 ml of acetic anhydride to 400 ml) is accurately added thereto. An air cooling tube is attached to the mouth of the flask and heated in a glycerin bath at 95-100 ° C. After 1 hour and 30 minutes, the mixture is cooled, 1 ml of purified water is added from an air condenser, and acetic anhydride is decomposed into acetic acid. Next, titration is performed with a 0.5 mol / L potassium hydroxide ethanol solution using a potentiometric titrator, and the inflection point of the obtained titration curve is set as the end point. Further, as a blank test, titration is performed without a sample, and an inflection point of the titration curve is obtained. The hydroxyl value is calculated by the following formula.

Hydroxyl value = {(BC) × f × 28.05 / X} + D
(Wherein B is the amount of 0.5 mol / L potassium hydroxide ethanol solution used in the blank test (ml), and C is the amount of 0.5 mol / L potassium hydroxide ethanol solution used in the titration (ml). F is a factor of 0.5 mol / L potassium hydroxide ethanol solution, D is an acid value, and 28.05 is 1/2 of 1 mol amount of potassium hydroxide 56.11)
As for the molecular weight of the polymer X, the weight average molecular weight is from 5,000 to 30,000, more preferably from 8,000 to 25,000.

  By setting the weight average molecular weight to 5,000 or more, it is preferable because the cellulose ester film has advantages such as less dimensional change under high temperature and high humidity and less curling as a polarizing plate protective film. When the weight average molecular weight is 30000 or less, the compatibility with the cellulose ester is further improved, and bleeding out under high temperature and high humidity, and further haze generation immediately after film formation is suppressed.

  The weight average molecular weight of the polymer X of the present invention can be adjusted by a known molecular weight adjusting method. Examples of such a molecular weight adjusting method include a method of adding a chain transfer agent such as carbon tetrachloride, lauryl mercaptan, octyl thioglycolate, and the like. The polymerization temperature is usually room temperature to 130 ° C., preferably 50 ° C. to 100 ° C., and this temperature or the polymerization reaction time can be adjusted.

  The measuring method of a weight average molecular weight can be based on the following method.

(Weight average molecular weight measurement method)
The weight average molecular weight is measured using high performance liquid chromatography.

  The measurement conditions are as follows.

Solvent: Methylene chloride Column: Shodex K806, K805, K803G (Used by connecting three Showa Denko Co., Ltd.)
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (manufactured by GL Sciences)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corp.) Mw = 100000-500 calibration curves with 13 samples were used. Thirteen samples are used at approximately equal intervals.

  The polymer Y of the present invention is a polymer having a weight average molecular weight of 500 or more and 3000 or less obtained by polymerizing an ethylenically unsaturated monomer Ya having no aromatic ring, and is a polymer represented by the following general formula (2). It is preferable.

  A weight average molecular weight of 500 or more is preferable because the residual monomer of the polymer is reduced. Moreover, it is preferable to set it as 3000 or less in order to maintain retardation value Rt fall performance.

General formula (2)
_{Ry- [CH 2 -C (-R 5} ) (- CO 2 R 6 -OH) -] k- [Yb] q-
(In the formula, R ₅ represents H or CH _3. R ₆ represents —CH ₂ —, —C ₂ H ₄ — or —C ₃ H ₆ —. Ry represents OH, H or a carbon number of 3 or less. Represents an alkyl group, Yb represents a monomer unit copolymerizable with Ya, k and q represent a molar composition ratio, provided that k ≠ 0 and k + q = 100.
The ethylenically unsaturated monomer Ya constituting the polymer Y obtained by polymerizing an ethylenically unsaturated monomer having no aromatic ring is, for example, methyl acrylate, ethyl acrylate, propyl acrylate (i- , N-), butyl acrylate (n-, i-, s-, t-), pentyl acrylate (n-, i-, s-), hexyl acrylate (n-, i-), heptyl acrylate (N-, i-), octyl acrylate (n-, i-), nonyl acrylate (n-, i-), myristyl acrylate (n-, i-), cyclohexyl acrylate, acrylic acid (2- Ethyl hexyl), acrylic acid (ε-caprolactone), acrylic acid (2-hydroxyethyl), acrylic acid (2-hydroxypropyl), acrylic acid (3-hydroxypropiyl) ), Acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl), methacrylic acid ester, the above acrylic acid ester changed to methacrylic acid ester; unsaturated acid, for example, acrylic acid, methacrylic acid , Maleic anhydride, crotonic acid, itaconic acid and the like.

  Yb is not particularly limited as long as it is an ethylenically unsaturated monomer copolymerizable with Ya. Examples of vinyl esters include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl valerate, vinyl pivalate, and vinyl caproate. Vinyl caprate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, vinyl cyclohexanecarboxylate, vinyl octylate, vinyl methacrylate, vinyl crotonate, vinyl sorbate, vinyl cinnamate and the like are preferred. Yb may be plural. k + q = 100, q is 0-30.

  The above-mentioned polymer X and polymer Y are both excellent in compatibility with cellulose ester, excellent in productivity without evaporation and volatilization, good retention as a protective film for polarizing plates, low moisture permeability, and dimensional stability. Are better.

The content of the polymer X and the polymer Y in the cellulose ester film is preferably in a range satisfying the following formulas (i) and (ii). When the content of the polymer X is Xg (mass% = the mass of the polymer X / the mass of the cellulose ester × 100) and the content of the polymer Y is Yg (mass%),
Formula (i) 5 ≦ Xg + Yg ≦ 35 (mass%)
Formula (ii) 0.05 ≦ Yg / (Xg + Yg) ≦ 0.4
A preferable range of the formula (i) is 10 to 25% by mass.

  If the total amount of the polymer X and the polymer Y is 5% by mass or more, the polymer X and the polymer Y sufficiently act to reduce the retardation value Rt. Moreover, if it is 35 mass% or less as a total amount, adhesiveness with polarizer PVA is favorable.

  The polymer X and the polymer Y can be directly added and dissolved as a material constituting the dope liquid described later, or can be added to the dope liquid after being previously dissolved in an organic solvent for dissolving the cellulose ester.

〔polyester〕
(Polyester represented by formula (3) or (4))
Cellulose of the present invention - scan ester film, or the polymer X and polymer Y, any of the polyester represented by the following general formula (3) or (4), contains a.

Formula _{(3) B 1 - (G} -A-) wG-B 1
(In the formula, B ₁ represents a monocarboxylic acid, G represents a divalent alcohol, A represents a dibasic acid, and B ₁ , G, and A do not contain an aromatic ring. W represents the number of repetitions. A plurality of B ₁ and G may be the same or different.)
Formula _{(4) B 2 - (A} -G-) zA-B 2
(In the formula, B ₂ represents a monoalcohol, G represents a divalent alcohol, A represents a dibasic acid, and B ₂ , G, and A do not contain an aromatic ring. Z represents the number of repetitions. The plurality of B ₂ and G may be the same or different.)
The monocarboxylic acids represented by B _1, is not particularly limited and includes known aliphatic monocarboxylic acids, can be used alicyclic monocarboxylic acid.

  Examples of preferred monocarboxylic acids include the following, but the present invention is not limited thereto.

  As the aliphatic monocarboxylic acid, a fatty acid having a straight chain or a side chain having 1 to 32 carbon atoms can be preferably used. The number of carbon atoms is more preferably 1-20, and particularly preferably 1-12. When acetic acid is contained, the compatibility with the cellulose ester is increased, and it is also preferable to use a mixture of acetic acid and another monocarboxylic acid.

  Preferred aliphatic monocarboxylic acids include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, 2-ethyl-hexanecarboxylic acid, undecylic acid, lauric acid, tridecyl Acids, myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, serotic acid, heptacosanoic acid, montanic acid, melicic acid, and laccelic acid, undecylenic acid And unsaturated fatty acids such as oleic acid, sorbic acid, linoleic acid, linolenic acid and arachidonic acid.

The monoalcohol component represented by B ₂ is not particularly limited, and known alcohols can be used. For example, an aliphatic saturated alcohol or aliphatic unsaturated alcohol having a straight chain or a side chain having 1 to 32 carbon atoms can be preferably used. The number of carbon atoms is more preferably 1-20, and particularly preferably 1-12.

  Examples of the divalent alcohol component represented by G include the following, but the present invention is not limited thereto. For example, ethylene glycol, diethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, 1,5-pentanediol, , 6-hexanediol, 1,5-pentylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, etc., among which ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol 1,2-butylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, 1,6-hexanediol, diethylene glycol and triethylene glycol are preferable, and 1,3-propylene glycol is more preferable. 1,4-butylene glycol 1,6-hexanediol, are used preferably diethylene glycol.

  The dibasic acid (dicarboxylic acid) component represented by A is preferably an aliphatic dibasic acid or an alicyclic dibasic acid. Examples of the aliphatic dibasic acid include malonic acid, succinic acid, glutaric acid, Adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedicarboxylic acid, dodecanedicarboxylic acid, etc., especially aliphatic dicarboxylic acids having 4 to 12 carbon atoms, at least one selected from these To do. That is, two or more dibasic acids may be used in combination.

  w and z represent the number of repetitions and are preferably 1 or more and 170 or less.

  The weight average molecular weight of the polyester is preferably 20000 or less, and more preferably 10,000 or less. In particular, polyesters having a weight average molecular weight of 500 to 10,000 have good compatibility with cellulose esters, and neither evaporation nor volatilization occurs during film formation.

  Polycondensation of polyester is performed by a conventional method. For example, a direct reaction of the above dibasic acid and glycol, the above dibasic acid or an alkyl ester thereof, for example, a polyesterification reaction or transesterification reaction between a dibasic acid methyl ester and a glycol, or a hot melt condensation method, Alternatively, it can be easily synthesized by any method of dehydrohalogenation reaction between acid chloride of these acids and glycol, but polyester having a weight average molecular weight not so large is preferably by direct reaction. Polyester having a high distribution on the low molecular weight side has very good compatibility with the cellulose ester, and after forming the film, it is possible to obtain a cellulose ester film having low moisture permeability and high transparency.

  A conventional method can be used as a method for adjusting the molecular weight without particular limitation. For example, although depending on the polymerization conditions, the amount of these monovalent compounds can be controlled by a method of blocking the molecular ends with a monovalent acid or monovalent alcohol. In this case, a monovalent acid is preferable from the viewpoint of polymer stability.

  For example, acetic acid, propionic acid, butyric acid and the like can be mentioned, but during the polycondensation reaction, they are not distilled out of the system, but are stopped and such monovalent acids are removed out of the reaction system. Those that are easily removed are sometimes selected, but these may be mixed and used. In the case of a direct reaction, the weight average molecular weight can also be adjusted by measuring the timing at which the reaction is stopped by the amount of water distilled off during the reaction. In addition, it can be adjusted by biasing the number of moles of glycol or dibasic acid to be charged or by controlling the reaction temperature.

  The polyester according to the present invention is preferably contained in an amount of 1 to 40% by mass with respect to the cellulose ester.

(Hard coat layer)
The polarizing plate protective film of the present invention is provided with a hard coat layer, and preferably a hard coat layer is provided on the cellulose ester film according to the present invention.

  The hard coat layer in the present invention is provided on one surface of the polarizing plate protective film.

  As the hard coat layer, an actinic radiation curable resin layer is preferably used.

  The actinic radiation curable resin layer refers to a layer mainly composed of a resin that cures through a crosslinking reaction or the like by irradiation with actinic rays such as ultraviolet rays or electron beams. As the actinic radiation curable resin, a component containing a monomer having an ethylenically unsaturated double bond is preferably used, and a hard coat layer is formed by curing by irradiation with actinic radiation such as ultraviolet rays or electron beams. Typical examples of the actinic radiation curable resin include an ultraviolet curable resin and an electron beam curable resin, and a resin curable by ultraviolet irradiation is preferable.

  As the ultraviolet curable resin, for example, an ultraviolet curable urethane acrylate resin, an ultraviolet curable polyester acrylate resin, an ultraviolet curable epoxy acrylate resin, an ultraviolet curable polyol acrylate resin, or an ultraviolet curable epoxy resin is preferable. Used. In particular, a urethane acrylate resin is preferable.

  The UV curable urethane acrylate resin generally contains 2-hydroxyethyl acrylate and 2-hydroxyethyl methacrylate (hereinafter referred to as acrylate) in addition to a product obtained by reacting a polyester polyol with an isocyanate monomer or a prepolymer. It can be easily obtained by reacting an acrylate monomer having a hydroxyl group such as 2-hydroxypropyl acrylate. For example, those described in JP-A-59-151110 can be used.

  For example, a mixture of 100 parts Unidic 17-806 (Dainippon Ink Co., Ltd.) and 1 part Coronate L (Nihon Polyurethane Co., Ltd.) is preferably used.

  Examples of UV curable polyester acrylate resins include those that are easily formed when 2-hydroxyethyl acrylate and 2-hydroxy acrylate monomers are generally reacted with polyester polyols. JP-A-59-151112 Can be used.

  Specific examples of the ultraviolet curable epoxy acrylate resin include an epoxy acrylate as an oligomer, a reactive diluent and a photoreaction initiator added thereto, and reacted to form an oligomer. The thing as described in 105738 can be used.

  Specific examples of UV curable polyol acrylate resins include trimethylolpropane triacrylate, ditrimethylolpropane tetraacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, alkyl-modified dipentaerythritol pentaacrylate, etc. I can list them.

  Specific examples of the photoreaction initiator of these ultraviolet curable resins include benzoin and its derivatives, acetophenone, benzophenone, hydroxybenzophenone, Michler's ketone, α-amyloxime ester, thioxanthone, and derivatives thereof. You may use with a photosensitizer. The photoinitiator can also be used as a photosensitizer. In addition, when using an epoxy acrylate photoinitiator, a sensitizer such as n-butylamine, triethylamine, or tri-n-butylphosphine can be used. The photoreaction initiator or photosensitizer used in the ultraviolet curable resin composition is 0.1 to 15 parts by weight, preferably 1 to 10 parts by weight, based on 100 parts by weight of the composition.

  Examples of the resin monomer include general monomers such as methyl acrylate, ethyl acrylate, butyl acrylate, benzyl acrylate, cyclohexyl acrylate, vinyl acetate, and styrene as monomers having one unsaturated double bond. In addition, monomers having two or more unsaturated double bonds include ethylene glycol diacrylate, propylene glycol diacrylate, divinylbenzene, 1,4-cyclohexane diacrylate, 1,4-cyclohexyldimethyl adiacrylate, and the above-mentioned trimethylolpropane. Examples thereof include triacrylate and pentaerythritol tetraacryl ester.

  Examples of commercially available ultraviolet curable resins that can be used in the present invention include ADEKA OPTMER KR / BY series: KR-400, KR-410, KR-550, KR-566, KR-567, BY-320B (Asahi Denka ( Co., Ltd.); Koeihard A-101-KK, A-101-WS, C-302, C-401-N, C-501, M-101, M-102, T-102, D-102, NS -101, FT-102Q8, MAG-1-P20, AG-106, M-101-C (manufactured by Guangei Chemical Co., Ltd.); Seika Beam PHC2210 (S), PHC X-9 (K-3), PHC2213, DP -10, DP-20, DP-30, P1000, P1100, P1200, P1300, P1400, P1500, P1600, SCR900 (manufactured by Dainichi Seika Kogyo Co., Ltd.) KRM7033, KRM7039, KRM7130, KRM7131, UVECRYL29201, UVECRYL29202 (manufactured by Daicel UCB); RC-5015, RC-5016, RC-5020, RC-5031, RC-5100, RC-5102, RC-5120 RC-5122, RC-5152, RC-5171, RC-5180, RC-5181 (manufactured by Dainippon Ink & Chemicals, Inc.); 340 clear (manufactured by China Paint Co., Ltd.); Sunrad H-601, RC-750, RC-700, RC-600, RC-500, RC-611, RC-612 (manufactured by Sanyo Chemical Industries); SP -1509, SP-1507 (manufactured by Showa Polymer Co., Ltd.); RCC-15C (manufactured by Grace Japan Co., Ltd.), Aronix M-6100, M-8030, M-8060 (manufactured by Toagosei Co., Ltd.), etc. Can be selected as appropriate.

  Specific examples of compounds include trimethylolpropane triacrylate, ditrimethylolpropane tetraacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, alkyl-modified dipentaerythritol pentaacrylate, and the like. .

  These actinic ray curable resin layers can be coated on a substrate by a known method such as a gravure coater, a dip coater, a reverse coater, a wire bar coater, a die coater, and an ink jet method.

As a light source for curing an ultraviolet curable resin by a photocuring reaction to form a cured coating layer, any light source that generates ultraviolet rays can be used without any limitation. For example, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a carbon arc lamp, a metal halide lamp, a xenon lamp, or the like can be used. These light sources are preferably air-cooled or water-cooled. Irradiation conditions vary depending on each lamp, but the irradiation amount of active rays is preferably 5 to 300 mJ / cm ² , particularly preferably 20 to 200 mJ / cm ² .

  Further, it is preferable to reduce the oxygen concentration to 0.01% to 2% by nitrogen purge in the irradiated portion.

  Moreover, when irradiating actinic radiation, it is preferable to carry out while applying tension | tensile_strength in the conveyance direction of a film, More preferably, it is performing applying tension | tensile_strength also in the width direction. The tension to be applied is preferably 30 to 300 N / m. The method for applying the tension is not particularly limited, and the tension may be applied in the conveying direction on the back roll, or the tension may be applied in the width direction or the biaxial direction by a tenter. This makes it possible to obtain a film having further excellent flatness.

  Examples of the organic solvent for the UV curable resin layer composition coating solution include hydrocarbons (toluene, xylene), alcohols (methanol, ethanol, isopropanol, butanol, cyclohexanol), ketones (acetone, methyl ethyl ketone, methyl isobutyl). Ketone), esters (methyl acetate, ethyl acetate, methyl lactate), glycol ethers, other organic solvents, or a mixture thereof. Propylene glycol monoalkyl ether (1 to 4 carbon atoms of the alkyl group) or propylene glycol monoalkyl ether acetate ester (1 to 4 carbon atoms of the alkyl group) is 5% by mass or more, more preferably 5 to 80%. It is preferable to use the organic solvent containing at least mass%.

  Moreover, it is preferable to add the silicon compound which has a surface active effect especially to a ultraviolet curable resin layer composition coating liquid. For example, polyether-modified silicone oil is preferably added. The number average molecular weight of the polyether-modified silicone oil is, for example, 1,000 to 100,000, preferably 2000 to 50,000. When the number average molecular weight is in the range of 10,000 to 100,000, the drying property of the coating film is fast, and the coating film This is preferable because it is difficult to bleed out to the surface.

  Commercially available silicon compounds include DKQ8-779 (trade name, manufactured by Dow Corning), SF3771, SF8410, SF8411, SF8419, SF8421, SF8428, SH200, SH510, SH1107, SH3749, SH3771, BX16-034, SH3746, SH3749, SH8400, SH3771M, SH3772M, SH3773M, SH3775M, BY-16-837, BY-16-839, BY-16-869, BY-16-870, BY-16-004, BY-16-891, BY-16 872, BY-16-874, BY22-008M, BY22-012M, FS-1265 (above, product names manufactured by Toray Dow Corning Silicone), KF-101, KF-100T, KF351, KF3 2, KF353, KF354, KF355, KF615, KF618, KF945, KF6004, Silicone X-22-945, X22-160AS (trade name, manufactured by Shin-Etsu Chemical Co., Ltd.), XF3940, XF3949 (trade name, manufactured by Toshiba Silicone Co., Ltd.) ), Disparon LS-009 (manufactured by Enomoto Kasei Co., Ltd.), Granol 410 (manufactured by Kyoeisha Yushi Chemical Co., Ltd.), TSF4440, TSF4441, TSF4445, TSF4446, TSF4452, TSF4460 (manufactured by GE Toshiba Silicone), BYK-306, BYK- 330, BYK-307, BYK-341, BYK-344, BYK-361 (manufactured by BYK-Japan) L series (for example, L7001, L-7006, L-7604, L-9000) manufactured by Nippon Unicar Co., Ltd. Y Over's, FZ series (FZ-2203, FZ-2206, FZ-2207) and the like, it is preferably used.

  As the compound having a surface active effect, other nonionic surfactants having an ethylene oxide chain can be added.

  These components enhance the applicability to the substrate and the lower layer. When added to the outermost surface layer of the laminate, it not only improves the water repellency, oil repellency and antifouling properties of the coating film, but also exhibits an effect on the scratch resistance of the surface. These components are preferably added in a range of 0.01 to 3% by mass with respect to the solid component in the coating solution.

  As a coating method of the ultraviolet curable resin composition coating solution, the above-described methods can be used. The coating amount is suitably 5 to 80 μm as a wet film thickness, and preferably 10 to 70 μm. The dry film thickness is 1 to 50 μm, preferably 1 to 30 μm.

  The dry film thickness of the hard coat layer is appropriately determined in consideration of the influence of heat of the backlight of the polarizing plate protective film.

The ultraviolet curable resin composition is preferably irradiated with ultraviolet rays during or after coating and drying, and the irradiation time for obtaining the active ray irradiation amount of 5 to 300 mJ / cm ² is from 0.1 seconds to 5 seconds. Minutes are good, and 0.1 to 10 seconds is more preferable from the viewpoint of curing efficiency or work efficiency of the ultraviolet curable resin.

Moreover, it is preferable that the illuminance of these active ray irradiation parts is 50-150 mW / cm < ² >.

  In order to prevent blocking, to improve scratch resistance, to give antiglare property or light diffusibility, and to adjust the refractive index in the cured resin layer thus obtained, fine particles of an inorganic compound or an organic compound Can also be added.

  It is preferable to add fine particles to the hard coat layer of the present invention. Examples of inorganic fine particles used include silicon oxide, titanium oxide, aluminum oxide, zirconium oxide, magnesium oxide, calcium carbonate, calcium carbonate, talc, clay, and calcined kaolin. And calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate and calcium phosphate. In particular, silicon oxide, titanium oxide, aluminum oxide, zirconium oxide, magnesium oxide and the like are preferably used.

  The organic fine particles include polymethacrylic acid methyl acrylate resin powder, acrylic styrene resin powder, polymethyl methacrylate resin powder, silicon resin powder, polystyrene resin powder, polycarbonate resin powder, benzoguanamine resin powder, melamine resin powder. Polyolefin resin powder, polyester resin powder, polyamide resin powder, polyimide resin powder, or polyfluoroethylene resin powder can be added to the ultraviolet curable resin composition. Particularly preferred are cross-linked polystyrene particles (for example, SX-130H, SX-200H, SX-350H, manufactured by Soken Chemical) and polymethyl methacrylate-based particles (for example, MX150, MX300, manufactured by Soken Chemical).

  The average particle size of these fine particle powders is preferably 0.005 to 10 μm, and particularly preferably 0.01 to 5 μm. As for the ratio of a ultraviolet curable resin composition and fine particle powder, it is desirable to mix | blend so that it may be 0.1-30 mass parts with respect to 100 mass parts of resin compositions.

  The ultraviolet curable resin layer may be a hard coat layer having a center line average roughness (Ra) defined by JIS B 0601 of 1 to 50 nm or an antiglare layer having an Ra of about 0.1 to 1 μm. preferable. The center line average roughness (Ra) is preferably measured with an optical interference type surface roughness measuring instrument, and can be measured using, for example, RST / PLUS manufactured by WYKO.

The hard coat layer of the present invention preferably contains an antistatic agent. Examples of the antistatic agent include Sn, Ti, In, Al, Zn, Si, Mg, Ba, Mo, W, and V. A conductive material containing at least one element selected from the group as a main component and having a volume resistivity of 10 ⁷ Ω · cm or less is preferable. Examples of the antistatic agent include metal oxides and composite oxides having the above elements.

Examples of metal oxides include, for example, ZnO, TiO ₂ , SnO ₂ , Al ₂ O ₃ , In ₂ O ₃ , SiO ₂ , MgO, BaO, MoO ₂ , V ₂ O ₅ , or complex oxides thereof. ZnO, In ₂ O ₃ , TiO ₂ and SnO ₂ are particularly preferable. Examples of containing different atoms include, for example, addition of Al and In to ZnO, addition of Nb and Ta to TiO ₂ , and addition of Sb, Nb and halogen elements to SnO ₂ . Addition is effective. The amount of these different atoms added is preferably in the range of 0.01 to 25 mol%, particularly preferably in the range of 0.1 to 15 mol%. In addition, the volume resistivity of these metal oxide powders having conductivity is 10 ⁷ Ω · cm or less, particularly 10 ⁵ Ω · cm or less.

(Cellulose ester)
In the cellulose ester film of the present invention, the cellulose ester as the main component is preferably a lower fatty acid ester of cellulose. The lower fatty acid in the lower fatty acid ester of cellulose means a fatty acid having 6 or less carbon atoms. For example, cellulose acetate, cellulose propionate, cellulose butyrate and the like, and JP-A-10-45804 and 8-231761 And mixed fatty acid esters such as cellulose acetate propionate and cellulose acetate butyrate as described in US Pat. No. 2,319,052 and the like. Among the above descriptions, the lower fatty acid esters of cellulose particularly preferably used are cellulose triacetate and cellulose acetate propionate. These cellulose esters can be used alone or in combination.

  In the case of cellulose triacetate, those having an average degree of acetylation (bound acetic acid amount) of 54.0 to 62.5% are preferably used, and more preferably cellulose having an average degree of acetylation of 58.0 to 62.5%. Triacetate.

  Preferred cellulose esters other than cellulose triacetate have an acyl group having 2 to 4 carbon atoms as a substituent, the substitution degree of the acetyl group is Ac, and the substitution degree of the fatty acid ester group of 3 to 4 carbon atoms is Pr. Sometimes, it is a cellulose ester that simultaneously satisfies the following formulas (III) and (IV).

(III) 2.1 ≦ Ac + Pr ≦ 2.9
(IV) 1.0 ≦ Ac ≦ 2.9
(However, Ac is the degree of substitution of the acetyl group, and Pr is the degree of substitution of the fatty acid ester group having 3 to 4 carbon atoms.)
Among these, cellulose acetate propionate satisfying 1.0 ≦ Ac ≦ 2.0 and 0.5 ≦ Pr ≦ 1.9 is preferable. The portion not substituted with an acyl group usually exists as a hydroxyl group. These can be synthesized by known methods.

  Moreover, these acyl group substitution degrees can be measured according to the method prescribed | regulated to ASTM-D817-96.

  As the cellulose ester, cellulose ester synthesized using cotton linter, wood pulp, kenaf or the like as a raw material can be used alone or in combination. In particular, it is preferable to use a cellulose ester synthesized from a cotton linter (hereinafter sometimes simply referred to as linter) alone or in combination.

  If the molecular weight of the cellulose ester is large, the rate of change of the elastic modulus due to heat becomes small, but if the molecular weight is too high, the viscosity of the cellulose ester solution becomes too high and the productivity is lowered. The molecular weight of the cellulose ester is preferably 30000-200000 in terms of number average molecular weight (Mn), more preferably 40000-170000.

  Moreover, when acquiring the effect of this invention, it is preferable that the value of ratio Mw / Mn of the weight average molecular weight (Mw) and number average molecular weight (Mn) of a cellulose ester is 1.4-3.0. In addition, More preferably, it is 1.7-2.2.

  The average molecular weight and molecular weight distribution of the cellulose ester can be measured by a known method using high performance liquid chromatography. Using this, the number average molecular weight and the weight average molecular weight can be calculated, and the ratio (Mw / Mn) can be calculated.

The measurement conditions are as follows.
Solvent: Methylene chloride column: Shodex K806, K805, K803G (used by connecting 3 products manufactured by Showa Denko KK)
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (manufactured by GL Sciences)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corp.) Mw = 100000-500 calibration curves with 13 samples were used. It is preferable to obtain 13 samples at approximately equal intervals.

  Cellulose ester was charged with 1 g in 20 ml of pure water (electric conductivity 0.1 μS / cm or less, pH 6.8), and stirred at 25 ° C. for 1 hr in a nitrogen atmosphere. The degree is preferably 1 to 100 μS / cm. If the pH is less than 6, the residual organic acid may accelerate cellulose degradation during heating and melting, and if the pH is higher than 7, hydrolysis may accelerate. In addition, when the electrical conductivity is 100 μS / cm or more, since a relatively large amount of residual ions are present, it is considered to be a factor for degrading cellulose during heating and melting.

(Plasticizer)
The dope used to form the cellulose ester film of the present invention is essentially free of conventionally used low molecular plasticizers, low molecular ultraviolet absorbers and low molecular antioxidants. However, if necessary, a small amount of a low-molecular plasticizer or a low-molecular ultraviolet absorber may be added to the extent that it does not precipitate, but the added plasticizer may be retardation Rt. A material that does not increase, for example, a material that does not have an aromatic ring is preferable.

  The following plasticizers can be used for the cellulose ester film of the present invention.

  Phosphate ester plasticizers: specifically, phosphoric acid alkyl esters such as triacetyl phosphate and tributyl phosphate, phosphoric acid cycloalkyl esters such as tricyclobenthyl phosphate and cyclohexyl phosphate, triphenyl phosphate, tricresyl phosphate And phosphoric acid aryl esters such as cresylphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate, trinaphthyl phosphate, trixylyl phosphate, tris ortho-biphenyl phosphate. These substituents may be the same or different, and may be further substituted. Further, it may be a mix of an alkyl group, a cycloalkyl group, and an aryl group, and the substituents may be covalently bonded.

  Also alkylene bis (dialkyl phosphate) such as ethylene bis (dimethyl phosphate), butylene bis (diethyl phosphate), alkylene bis (diaryl phosphate) such as ethylene bis (diphenyl phosphate), propylene bis (dinaphthyl phosphate), phenylene bis (dibutyl phosphate) ), Arylene bis (dialkyl phosphate) such as biphenylene bis (dioctyl phosphate), phosphate esters such as arylene bis (diaryl phosphate) such as phenylene bis (diphenyl phosphate) and naphthylene bis (ditoluyl phosphate). These substituents may be the same or different, and may be further substituted. Further, it may be a mix of an alkyl group, a cycloalkyl group, and an aryl group, and the substituents may be covalently bonded.

  Furthermore, the phosphate ester partial structure may be part of the polymer or regularly pendant, and may be introduced into part of the molecular structure of additives such as antioxidants, acid scavengers, and UV absorbers. May be. Among the above-mentioned compounds, phosphoric acid aryl ester and arylene bis (diaryl phosphate) are preferable, and specifically, triphenyl phosphate and phenylene bis (diphenyl phosphate) are preferable.

  Ethylene glycol ester plasticizer: Specifically, ethylene glycol alkyl ester plasticizers such as ethylene glycol diacetate and ethylene glycol dibutyrate, ethylene glycol dicyclopropyl carboxylate, ethylene glycol dicyclohexyl carboxylate and the like Examples include ethylene glycol cycloalkyl ester plasticizers and ethylene glycol aryl ester plasticizers such as ethylene glycol dibenzoate and ethylene glycol di4-methylbenzoate. These alkylate groups, cycloalkylate groups, and arylate groups may be the same or different, and may be further substituted. Further, a mixture of alkylate group, cycloalkylate group and arylate group may be used, and these substituents may be covalently bonded. Further, the ethylene glycol part may be substituted, the ethylene glycol ester partial structure may be part of the polymer or regularly pendant, and the antioxidant, acid scavenger, UV absorber, etc. It may be introduced into a part of the molecular structure of the additive.

  Glycerin ester plasticizers: Specifically, glycerol alkyl esters such as triacetin, tributyrin, glycerol diacetate caprylate, glycerol oleate propionate, and glycerin cycloalkyl esters such as glycerol tricyclopropyl carboxylate and glycerol tricyclohexyl carboxylate Glyceryl aryl esters such as glycerin tribenzoate and glycerin 4-methylbenzoate, diglycerin tetraacetylate, diglycerin tetrapropionate, diglycerin acetate tricaprylate, diglycerin alkyl esters such as diglycerin tetralaurate, di Diglycerides such as glycerin tetracyclobutylcarboxylate and diglycerin tetracyclopentylcarboxylate Emissions cycloalkyl esters, diglycerin tetrabenzoate, diglycerin aryl ester such as diglycerin 3-methylbenzoate or the like. These alkylate groups, cycloalkylcarboxylate groups, and arylate groups may be the same or different, and may be further substituted.

  Further, it may be a mix of alkylate group, cycloalkylcarboxylate group, and arylate group, and these substituents may be bonded by a covalent bond. Furthermore, the glycerin and diglycerin part may be substituted, the partial structure of the glycerin ester and the diglycerin ester may be part of the polymer or regularly pendant, and an antioxidant, an acid scavenger, It may be introduced into a part of the molecular structure of an additive such as an ultraviolet absorber.

  Polyhydric alcohol ester plasticizer: Specifically, alkyl polyhydric carboxylic acid alkyl ester plasticizer such as tridodecyl tricarbarate, tributyl-meso-butane-1,2,3,4-tetracarboxylate , Alkyl polyvalent carboxylic acid cycloalkyl ester plasticizers such as tricyclohexyl tricarbarate and tricyclopropyl-2-hydroxy-1,2,3-propanetricarboxylate, triphenyl 2-hydroxy-1,2, Alkyl polyvalent carboxylic acid aryl ester plasticizers such as 3-propanetricarboxylate and tetra-3-methylphenyltetrahydrofuran-2,3,4,5-tetracarboxylate, tetrahexyl-1,2,3,4- Cyclobutane tetracarboxylate, tetrabutyl-1,2, 1,4-cyclopentanetetracarboxylate and other cycloalkyl polycarboxylic acid alkyl ester plasticizers, tetracyclopropyl-1,2,3,4-cyclobutanetetracarboxylate, tricyclohexyl-1,3,5-cyclohexyl Cycloalkyl polycarboxylic acid cycloalkyl ester plasticizers such as tricarboxylate, triphenyl-1,3,5-cyclohexyl tricarboxylate, hexa-4-methylphenyl-1,2,3,4,5,6 -Cycloalkyl polycarboxylic acid aryl ester plasticizers such as cyclohexyl hexacarboxylate, tridodecylbenzene-1,2,4-tricarboxylate, tetraoctylbenzene-1,2,4,5-tetracarboxylate, etc. Aryl polycarboxylic acid Lester ester plasticizer, aryl polyvalent carboxylic acid cycloalkyl ester plasticizer tri such as tricyclopentylbenzene-1,3,5-tricarboxylate, tetracyclohexylbenzene-1,2,3,5-tetracarboxylate Aryl polycarboxylic acid aryl ester-based plasticizers such as phenylbenzene-1,3,5-tetracartoxylate and hexa-4-methylphenylbenzene-1,2,3,4,5,6-hexacarboxylate Can be mentioned. These alkoxy groups and cycloalkoxy groups may be the same or different, may be mono-substituted, and these substituents may be further substituted. The alkyl group and cycloalkyl group may be mixed, and these substituents may be bonded together by a covalent bond. Further, the aromatic ring of phthalic acid may be substituted, and a multimer such as a dimer, trimer or tetramer may be used. In addition, the partial structure of phthalate ester may be part of the polymer or may be regularly pendant to the polymer, and introduced into part of the molecular structure of additives such as antioxidants, acid scavengers, UV absorbers, etc. May be.

  Dicarboxylic acid ester plasticizers: Specifically, alkyldocarboxylic acid alkyl ester plasticizers such as didodecyl malonate (C1), dioctyl adipate (C4), dibutyl sebacate (C8), dicyclopentyl succinate, Alkyl dicarboxylic acid cycloalkyl ester plasticizers such as dicyclohexyl adipate, alkyl dicarboxylic acid aryl ester plasticizers such as diphenyl succinate and di4-methylphenyl glutarate, dihexyl-1,4-cyclohexanedicarboxylate, Cycloalkyldicarboxylic acid alkyl ester plasticizers such as didecylbicyclo [2.2.1] heptane-2,3-dicarboxylate, dicyclohexyl-1,2-cyclobutanedicarboxylate, dicyclopropyl-1,2 Cycloalkyldicarboxylic acid cycloalkyl ester plasticizers such as cyclohexyl dicarboxylate, aryl cycloalkyldicarboxylates such as diphenyl-1,1-cyclopropyldicarboxylate, di2-naphthyl-1,4-cyclohexanedicarboxylate Ester plasticizers, aryl dicarboxylic acid alkyl ester plasticizers such as diethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate and di-2-ethylhexyl phthalate, and aryl dicarboxylic acid cycloalkyls such as dicyclopropyl phthalate and dicyclohexyl phthalate Examples include ester plasticizers and aryl dicarboxylic acid aryl ester plasticizers such as diphenyl phthalate and di4-methylphenyl phthalate. These alkoxy groups and cycloalkoxy groups may be the same or different, may be mono-substituted, and these substituents may be further substituted. The alkyl group and cycloalkyl group may be mixed, and these substituents may be bonded together by a covalent bond. Further, the aromatic ring of phthalic acid may be substituted, and a multimer such as a dimer, trimer or tetramer may be used. In addition, the partial structure of phthalate ester may be part of the polymer or may be regularly pendant to the polymer, and introduced into part of the molecular structure of additives such as antioxidants, acid scavengers, UV absorbers, etc. May be.

  Polycarboxylic acid ester plasticizers: Specifically, alkyl polycarboxylic acid alkyl ester plastics such as tridodecyl tricarbarate and tributyl-meso-butane-1,2,3,4-tetracarboxylate Agents, alkyl polyvalent carboxylic acid cycloalkyl ester type plasticizers such as tricyclohexyl tricarbarate, tricyclopropyl-2-hydroxy-1,2,3-propanetricarboxylate, triphenyl 2-hydroxy-1,2 Alkyl polycarboxylic acid aryl ester plasticizers such as 1,3-propanetricarboxylate, tetra-3-methylphenyltetrahydrofuran-2,3,4,5-tetracarboxylate, tetrahexyl-1,2,3,4 -Cyclobutane tetracarboxylate, tetrabutyl-1,2, 1,4-cyclopentanetetracarboxylate and other cycloalkyl polycarboxylic acid alkyl ester plasticizers, tetracyclopropyl-1,2,3,4-cyclobutanetetracarboxylate, tricyclohexyl-1,3,5-cyclohexyl Cycloalkyl polycarboxylic acid cycloalkyl ester plasticizers such as tricarboxylate, triphenyl-1,3,5-cyclohexyl tricarboxylate, hexa-4-methylphenyl-1,2,3,4,5,6 -Cycloalkyl polycarboxylic acid aryl ester plasticizers such as cyclohexyl hexacarboxylate, tridodecylbenzene-1,2,4-tricarboxylate, tetraoctylbenzene-1,2,4,5-tetracarboxylate, etc. Aryl polycarboxylic acid Lester ester plasticizer, aryl polyvalent carboxylic acid cycloalkyl ester plasticizer tri such as tricyclopentylbenzene-1,3,5-tricarboxylate, tetracyclohexylbenzene-1,2,3,5-tetracarboxylate Aryl polycarboxylic acid aryl ester-based plasticizers such as phenylbenzene-1,3,5-tetracartoxylate and hexa-4-methylphenylbenzene-1,2,3,4,5,6-hexacarboxylate Can be mentioned. These alkoxy groups and cycloalkoxy groups may be the same or different, may be mono-substituted, and these substituents may be further substituted. The alkyl group and cycloalkyl group may be mixed, and these substituents may be bonded together by a covalent bond. Further, the aromatic ring of phthalic acid may be substituted, and a multimer such as a dimer, trimer or tetramer may be used. In addition, the partial structure of phthalate ester may be part of the polymer or may be regularly pendant to the polymer, and introduced into part of the molecular structure of additives such as antioxidants, acid scavengers, UV absorbers, etc. May be.

(UV absorber)
The polarizing plate protective film and other films used in the liquid crystal image display device contain an ultraviolet absorber, and the ultraviolet absorber serves to prevent deterioration of the liquid crystal and the polarizing film when used outdoors. In the cellulose ester film of the present invention, an ultraviolet absorber is preferably used. The ultraviolet absorber is excellent in the performance of absorbing ultraviolet light having a wavelength of 370 nm or less, absorbs as little visible light as possible in a wavelength of 400 nm or more, and preferably has a transmittance of 50% or more. In particular, the transmittance at a wavelength of 370 nm is preferably 10% or less, and more preferably 5% or less. Examples of ultraviolet absorbers that can be used in the present invention include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, and the like. A benzotriazole-based compound with little coloring is preferable. Benzotriazole ultraviolet absorbers and benzophenone ultraviolet absorbers having stability against light are preferable, and benzotriazole ultraviolet absorbers with less unnecessary coloring are particularly preferable. For example, TINUVIN109, TINUVIN171, TINUVIN326, TINUVIN327, TINUVIN328, etc., manufactured by Ciba Specialty Chemicals Co., Ltd. can be preferably used. Or may volatilize, the amount added is 1 to 10% by mass.

  In the present invention, it is more preferable that a high molecular weight ultraviolet absorber that is less likely to precipitate than the above low molecular weight ultraviolet absorber is contained in the cellulose ester film together with the polymer according to the present invention. Ultraviolet rays can be sufficiently cut in a stable state without impairing the wetness and without phase separation in the film. As the polymer ultraviolet absorber useful in the present invention, the polymer ultraviolet absorber described in JP-A-6-148430 and a polymer containing an ultraviolet absorber monomer can be used without limitation.

  The ultraviolet absorbent, ultraviolet absorbent monomer and intermediate thereof used in the present invention can be synthesized with reference to known literature. For example, U.S. Pat. Nos. 3,072,585, 3,159,646, 3,399,173, 3,761,272, 4,028,331, 5,683,861 No., European Patent No. 86,300,416, JP-A Nos. 63-227575, 63-185969, Polymer Bulletin. V. 20 (2), 169-176, and Chemical Abstracts V.I. 109, no. 191389 and the like can be synthesized.

  The ultraviolet absorbent and ultraviolet absorbent polymer used in the present invention can be used together with a low molecular compound, a high molecular compound, an inorganic compound, or the like, if necessary, when mixed with another transparent polymer. For example, the ultraviolet absorber used in the present invention and other low molecular ultraviolet absorbers are simultaneously mixed with another transparent polymer, or the ultraviolet absorbent polymer and other low molecular ultraviolet absorber used in the present invention are mixed, It is also one of preferred embodiments to mix with another transparent polymer at the same time. Similarly, it is one of preferred embodiments to simultaneously mix additives such as an antioxidant, a plasticizer, and a flame retardant.

  The method for adding the ultraviolet absorbent and ultraviolet absorbent polymer used in the present invention to the cellulose ester film may be contained in the cellulose ester film, or may be applied onto the cellulose ester film. When it is contained in the cellulose ester film, it may be added directly or in-line. In-line addition is a method in which an in-line mixer or the like is added to the dope composition after dissolving in advance in an organic solvent (for example, methanol, ethanol, methylene chloride, etc.).

The amount of the ultraviolet absorber and the ultraviolet absorbing polymer used in the present invention is not uniform depending on the kind of the compound, the usage conditions, etc., but in the case of an ultraviolet absorber, it is 0.2 per 1 m ^{2 of} the cellulose ester film. -3.0 g is preferable, 0.4-2.0 is more preferable,
0.5 to 1.5 is particularly preferable. Moreover, when it is a ultraviolet absorption polymer, 0.6-9.0g is preferable per 1 m < ² > of cellulose-ester films, 1.2-6.0 are still more preferable, 1.5-3.0 are especially preferable.

  Furthermore, from the viewpoint of preventing liquid crystal deterioration, those having excellent ultraviolet absorption performance at a wavelength of 380 nm or less and low visible light absorption of 400 nm or more are preferable from the viewpoint of good liquid crystal display properties. In the present invention, the transmittance at a wavelength of 380 nm is particularly preferably 8% or less, more preferably 4% or less, and particularly preferably 1% or less.

  As a commercially available UV absorber monomer that can be used in the present invention, UVM-1 1- (2-benzotriazole) -2-hydroxy-5- (2-vinyloxycarbonylethyl) benzene, manufactured by Otsuka Chemical Co., Ltd. 1- (2-benzotriazole) -2-hydroxy-5- (2-methacryloyloxyethyl) benzene of the reactive ultraviolet absorber RUVA-93, or an analog thereof. A polymer or copolymer obtained by singly or copolymerizing these is also preferably used, but is not limited thereto. For example, as a commercially available polymer ultraviolet absorber, PUVA-30M manufactured by Otsuka Chemical Co., Ltd. is preferably used. Two or more kinds of ultraviolet absorbers may be used. The ultraviolet absorber may be added to the dope after the ultraviolet absorber is dissolved in an organic solvent such as alcohol, methylene chloride, dioxolane, or methyl acetate, or may be added directly into the dope composition.

  Moreover, the cellulose ester film of the present invention may contain an antioxidant. For example, it may contain a peroxide decomposing agent, a radical chain inhibitor, a metal deactivator or an acid scavenger as described in JP-A-5-197073. The amount of these compounds added is preferably 1 ppm to 1.0%, more preferably 10 to 1000 ppm in terms of mass ratio with respect to the cellulose ester.

  In the present invention, the cellulose ester film preferably contains a fine particle matting agent. Examples of the fine particle matting agent include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, kaolin, talc, and baking. It is preferable to contain inorganic fine particles such as calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, calcium phosphate, and crosslinked polymer fine particles. Of these, silicon dioxide is preferable because it can reduce the haze of the film. The average particle size of the secondary particles of the fine particles is in the range of 0.01 to 1.0 μm, and the content is preferably 0.005 to 0.3% by mass with respect to the cellulose ester. In many cases, fine particles such as silicon dioxide are surface-treated with an organic material, but such a material is preferable because it can reduce the haze of the film. Preferred organic substances for the surface treatment include halosilanes, alkoxysilanes (particularly alkoxysilanes having a methyl group), silazane, siloxane and the like. The larger the average particle size of the fine particles, the greater the mat effect, and on the contrary, the smaller the average particle size, the better the transparency. Therefore, the average particle size of the preferred primary particles is 5 to 50 nm, more preferably 7 to 16 nm. It is. These fine particles are usually present as aggregates in the cellulose ester film, and it is preferable to form irregularities of 0.01 to 1.0 μm on the surface of the cellulose ester film. As the fine particles of silicon dioxide, AEROSIL 200, 200V, 300, R972, R972V, R974, R202, R812, OX50, TT600, etc. manufactured by Aerosil Co., Ltd. can be mentioned, preferably AEROSIL 200V, R972, R972V, R974, R202 and R812. Two or more of these matting agents may be used in combination. When using 2 or more types together, it can mix and use in arbitrary ratios. In this case, matting agents having different average particle sizes and materials, for example, AEROSIL 200V and R972V can be used in a mass ratio of 0.1: 99.9 to 99.9 to 0.1.

  Next, the manufacturing method of the cellulose-ester film of this invention is described.

  A method for preparing a cellulose ester dope in the present invention will be described. The dough is formed by dissolving the flaky cellulose ester in an organic solvent mainly containing a good solvent for the cellulose ester in a dissolving kettle while stirring. For dissolution, a method carried out at normal pressure, a method carried out below the boiling point of the main solvent, a method carried out under pressure above the boiling point of the main solvent, JP-A-9-95544, 9-95557 or 9-95538 There are various dissolution methods, such as a method performed by the cooling dissolution method as described in JP-A No. 11-21379, and a method performed at a high pressure as described in JP-A No. 11-21379. After dissolution, the dope is filtered with a filter medium, defoamed, and sent to the next process with a pump. The concentration of the cellulose ester in the dope is about 10 to 35% by mass. More preferably, it is 15-25 mass%. In order to contain the polymer useful in the present invention in the cellulose ester dope, the addition method such as addition after dissolving the polymer in an organic solvent in advance or direct addition to the cellulose ester dope can be carried out without limitation. In this case, the polymer is added so as not to become cloudy or phase-separated in the dope. The amount added is as described above.

  Examples of organic solvents as good solvents for cellulose esters include methyl acetate, ethyl acetate, amyl acetate, ethyl formate, acetone, cyclohexanone, methyl acetoacetate, tetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, 1,4-dioxane, 2,2,2-trifluoroethanol, 2,2,3,3-hexafluoro-1-propanol, 1,3-difluoro-2-propanol, 1,1,1,3,3 , 3-hexafluoro-2-methyl-2-propanol, 1,1,1,3,3,3-hexafluoro-2-propanol, 2,2,3,3,3-pentafluoro-1-propanol, Nitroethane, 2-pyrrolidone, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, methylene chloride, Etc. can be mentioned Romopuropan, methyl acetate, acetone, it is preferably used methylene chloride.

  However, non-chlorine organic solvents tend to be preferable due to recent environmental problems. In addition, it is preferable to use a lower alcohol such as methanol, ethanol or butanol in combination with these organic solvents because the solubility of the cellulose ester in the organic solvent can be improved and the dope viscosity can be reduced. In particular, ethanol having a low boiling point and low toxicity is preferred.

  The organic solvent used for the dope used in the present invention is preferably used by mixing a good solvent and a poor solvent of cellulose ester in terms of production efficiency, and the preferred range of the mixing ratio of the good solvent and the poor solvent is The good solvent is 70 to 98% by mass, and the poor solvent is 2 to 30% by mass. With the good solvent and the poor solvent used in the present invention, those that dissolve the cellulose ester used alone are defined as good solvents, and those that do not dissolve alone are defined as poor solvents.

  Although it does not specifically limit as a poor solvent used for dope used for this invention, For example, methanol, ethanol, n-butanol, cyclohexane, acetone, cyclohexanone etc. can be used preferably. Also for the polymer according to the present invention, the organic solvent is preferably selected using a good solvent for cellulose ester. As described above, when using a low molecular plasticizer, it can be carried out by a normal addition method, either directly added into the dope, or dissolved in an organic solvent in advance and poured into the dope. Good.

  In the present invention, when various additives as described above are added to the cellulose ester dope, the cellulose ester dope and various additives can be added in-line to a solution in which a small amount of cellulose ester is dissolved and mixed. preferable. For example, it is preferable to use an in-line mixer such as a static mixer SWJ (Toray static type in-pipe mixer Hi-Mixer) (manufactured by Toray Engineering). When using an in-line mixer, it is preferable to apply it to a dope in which cellulose ester is concentrated and dissolved under high pressure. The type of the pressure vessel is not particularly limited and can withstand a predetermined pressure, and heated and stirred under pressure. If you can.

  In the present invention, the cellulose ester dope must be filtered to remove foreign matters, particularly foreign matters that can be recognized as images in a liquid crystal image display device. It can be said that the quality of the protective film for polarizing plates is determined by this filtration. Filter media used for filtration preferably have a low absolute filtration accuracy, but if the absolute filtration accuracy is too small, the filter media is likely to be clogged, and the filter media must be frequently replaced, reducing productivity. There is a problem. For this reason, the cellulose ester-doped filter medium of the present invention preferably has an absolute filtration accuracy of 0.008 mm or less, more preferably in the range of 0.001 to 0.008 mm, and in the range of 0.003 to 0.006 mm. Further preferred.

There are no particular restrictions on the material of the filter medium, and ordinary filter media can be used. However, filter fibers made of plastic fibers such as polypropylene and Teflon (registered trademark) and metal filter media such as stainless steel fibers can cause the fibers to fall off. Less preferred. Filtration of the cellulose ester dope of the present invention can be carried out by a usual method, but the method of filtration while heating under pressure at a temperature not lower than the boiling point of the solvent at a normal pressure and in a range where the solvent does not boil is used before and after the filtration. The increase in differential pressure (hereinafter sometimes referred to as filtration pressure) is small and preferable. A preferred temperature range is 45 to 120 ° C, more preferably 45 to 70 ° C, and still more preferably 45 to 55 ° C. A smaller filtration pressure is preferred. The filtration pressure is preferably 1.6 × 10 ⁶ Pa or less, more preferably 1.2 × 10 ⁶ Pa or less, and further preferably 1.0 × 10 ⁶ Pa or less.

  If the cellulose of the raw material contains an acyl group unsubstituted or low-substituted cellulose ester, a foreign matter failure (hereinafter sometimes referred to as a bright spot) may occur. When a cellulose ester film is placed between two polarizing plates in a crossed state (crossed nicols), light is irradiated from one side and observed with an optical microscope (50 times) from the opposite side, a normal cellulose ester film is obtained. If there is, the light is blocked and you can't see anything black, but if there is a foreign object, the light leaks out and appears to shine like a spot. The larger the diameter of the bright spot, the greater the actual harm in the case of a liquid crystal image display device, preferably 50 μm or less, more preferably 10 μm or less, and even more preferably 8 μm or less.

The diameter of the bright spot means a value obtained by calculating the projected area of the bright spot as the diameter of a perfect circle having the same area. There are no practical problems as long as the bright spot has a diameter of 400 / cm ² or less, but 300 / cm ² or less is preferable, and 200 / cm ² or less is more preferable. In order to reduce the number and size of such bright spots, it is necessary to sufficiently filter fine foreign matters. In addition, as described in JP-A-2000-137115, a method of re-adding a pulverized product of a cellulose ester film once formed into a dope and using it as a raw material for cellulose ester and its additive is a bright spot. Since it can reduce, it can use preferably.

  Next, the process of casting the cellulose ester dope on the metal support, the drying process on the metal support, and the peeling process of peeling the web from the metal support will be described. The metal support is an endless metal belt or a rotating metal drum that moves indefinitely, and its surface is a mirror surface. The casting step is a step of feeding the dope as described above to a pressure die through a pressure type quantitative gear pump and casting the dope from the pressure die onto the metal support at the casting position. Other casting methods include a doctor blade method in which the film thickness of the cast dope film is adjusted with a blade, or a reverse roll coater method in which the film is adjusted with a reverse-rotating roll, but the slit shape of the die part is adjusted. A pressure die that is easy to make uniform in film thickness is preferable. Examples of the pressure die include a coat hanger die and a T die, and any of them is preferably used. In order to increase the film forming speed, two or more pressure dies may be provided on the metal support, and the dope amount may be divided and stacked. In order to adjust the film thickness, it is preferable to control the dope concentration, the pumped liquid amount, the slit gap of the die base, the extrusion pressure of the die, the speed of the metal support, etc. so as to obtain a desired thickness.

  The drying process on the metal support is a process in which the web (the dope film after casting on the metal support is referred to as the web) is heated on the support to evaporate the solvent. In order to evaporate the solvent, there are a method in which heated air is blown from the web side and the back side of the support, a method in which heat is transferred from the back side of the support by a heated liquid, a method in which heat is transferred from the front and back by radiant heat, and the like. A method of combining them is also preferable. Moreover, if the film thickness of a web is thin, drying will be quick. The temperature of the metal support may be the same or different depending on the position.

  In the drying method on the metal support suitable for the present invention, for example, the metal support is preferably cast at a temperature of 0 to 40 ° C., preferably 5 to 30 ° C. The drying air applied to the web is preferably about 30 to 45 ° C, but is not limited thereto.

  The peeling step is a step of evaporating the organic solvent on the metal support and peeling the web before the metal support goes around, and then the web is sent to the drying step. The position at which the web is peeled from the metal support is called the peeling point, and the roll that helps the peeling is called the peeling roll. Although it depends on the thickness of the web, if the residual solvent amount of the web at the peeling point (the following formula) is too large, it will be difficult to peel, or conversely if it is peeled off after sufficiently drying on the support, May be peeled off. Usually, the web is peeled at a residual solvent amount of 20 to 180% by mass.

  In the present invention, the preferable amount of residual solvent for peeling is 20 to 40% by mass or 60 to 150% by mass, and particularly preferably 80 to 140% by mass. As a method for increasing the film forming speed (the film forming speed can be increased because the film is peeled off while the residual solvent amount is as large as possible), there is a gel casting method (gel casting) that can be peeled even when the residual solvent amount is large. As the method, there are a method of adding a poor solvent for the cellulose ester in the dope and casting the dope and then gelling, a method of reducing the temperature of the support and gelling. There is also a method of adding a metal salt in the dope. By gelling on the support and strengthening the film, it is possible to speed up the peeling and increase the film forming speed. When peeling at a time when the amount of residual solvent is larger, if the web is too soft, the flatness at the time of peeling will be impaired, or slippage and vertical stripes due to peeling tension will tend to occur, and the amount of residual solvent is determined by the balance between economic speed and quality. It is done.

  The amount of residual solvent used in the present invention can be expressed by the following formula.

Residual solvent amount (% by mass) = {(MN) / N} × 100
Here, M is the mass of the web at any point, and N is the mass when M is dried at 110 ° C. for 3 hours.

  Moreover, in the drying process of the cellulose ester film, it is preferable to further dry the film peeled off from the support, and to make the residual solvent amount 2.0% by mass or less, more preferably 1.0% by mass, and still more preferably. , 0.5% by mass or less.

  In the web drying process, a roll drying apparatus in which rolls are arranged in a staggered manner, and a method of drying while conveying the web with a tenter drying apparatus that holds the width of the web with clips and holds the width or extends slightly in the width direction are adopted. In the present invention, it is particularly preferable because the humidity stability of the optical performance is improved by maintaining the width or stretching in an arbitrary process after peeling from the support of the tenter drying apparatus and in an arbitrary amount of residual solvent. The means for drying the web is not particularly limited, and is generally performed by hot air, infrared rays, a heating roll, microwaves, or the like. It is preferable to carry out with hot air in terms of simplicity. The drying temperature is preferably increased stepwise in the range of 40 to 180 ° C, and more preferably in the range of 50 to 160 ° C. Moreover, since there exists an effect which reduces retardation value Rt and Ro, it is preferable to take the drying time at high temperature for a long time.

  The cellulose ester film of the present invention is preferably stretched by 1% or more in both MD (film transport direction) / TD (direction perpendicular to the transport direction) in order to ensure flatness. In the case of producing a film having no in-plane retardation, it is preferable that the MD stretching ratio and the TD stretching ratio are close, but the MD and TD stretching ratios may be different. However, since the retardation value Rt becomes lower as the sum of the MD stretching ratio and the TD stretching ratio becomes smaller, it is appropriately adjusted. Further, from the viewpoint of the effect of reducing Rt, it is preferable to carry out at a high temperature during any stretching.

  The stretching operation may be performed in multiple stages, and it is preferable to perform biaxial stretching in the casting direction and the width direction. Also, when biaxial stretching is performed, simultaneous biaxial stretching may be performed or may be performed stepwise. In this case, stepwise means that, for example, stretching in different stretching directions can be sequentially performed, stretching in the same direction is divided into multiple stages, and stretching in different directions is added to any one of the stages. Is also possible.

  Although the film thickness of the cellulose ester film used for the polarizing plate protective film of the present invention cannot be uniquely determined because of the heat resistance due to the heat of the backlight, generally 10 to 100 μm is preferable, and 10 to 80 μm is preferable. Further preferred is 15-60 μm. In many cases, it is thicker than the hard coat layer provided on the outermost layer of the liquid crystal display device due to scratch resistance and the like.

  The width of the cellulose ester film is preferably 1.4 m or more, and preferably in the range of 1.4 m to 4 m for a large-sized liquid crystal display device from the viewpoint of productivity.

  The cellulose ester film of the present invention is suitable for a polarizing plate protective film used in a transverse electric field switching mode type (also referred to as IPS mode type) liquid crystal display device, and has retardation values Ro and Rt of 0 nm ≦ Ro ≦ 10 nm and − It is in the range of 20 nm ≦ Rt ≦ 20 nm.

Formula (I) Ro = (nx−ny) × d
Formula (II) Rt = {(nx + ny) / 2−nz} × d
(Here, the refractive index in the slow axis direction in the plane of the polarizing plate protective film is nx, the refractive index in the direction perpendicular to the slow axis in the plane is ny, and the refractive index in the thickness direction of the film is nz, d. Represents the thickness (nm) of the film.)
The retardation values Ro and Rt can be measured using an automatic birefringence meter. For example, it can be obtained under an environment of 23 ° C. and 55% RH using KOBRA-21ADH (Oji Scientific Instruments).

(Polarizer)
The polarizing plate of the present invention and the liquid crystal display device of the present invention using the polarizing plate will be described.

<Polarizer>
A polarizer, which is a main component of a polarizing plate, is an element that transmits only light having a plane of polarization in a certain direction. A typical polarizing film known at present is a polyvinyl alcohol polarizing film, which is a polyvinyl alcohol. There are one in which iodine is dyed on a system film and one in which dichroic dye is dyed.

  In the present invention, the film is formed from ethylene-modified polyvinyl alcohol having an ethylene unit content of 1 to 4 mol%, a polymerization degree of 2000 to 4000, a saponification degree of 99.0 to 99.99 mol%, and a hot water cutting temperature of 66 to An ethylene-modified polyvinyl alcohol film having a temperature of 73 ° C. is also preferably used. Further, it is more preferable that the difference in hot water cutting temperature between two points 5 cm apart in the TD direction of the film is 1 ° C. or less, and further two points 1 cm apart in the TD direction of the film. In order to reduce color spots, it is more preferable that the difference in hot water cutting temperature between them is 0.5 ° C. or less. Furthermore, it is particularly preferable that the thickness of the film is 10 to 50 μm in order to reduce color spots.

  As the ethylene-modified polyvinyl alcohol (ethylene-modified PVA) used in the present invention, an ethylene-vinyl ester polymer obtained by copolymerizing ethylene and a vinyl ester monomer is saponified, and the vinyl ester unit is converted into a vinyl alcohol unit. Can be used. Examples of the vinyl ester monomers include vinyl formate, vinyl acetate, vinyl propionate, vinyl valelate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pivalate, vinyl versatate, and the like. Of these, vinyl acetate is preferably used.

  The ethylene unit content (ethylene copolymerization amount) in the ethylene-modified PVA is 1 to 4 mol%, preferably 1.5 to 3 mol%, more preferably 2 to 3 mol%. When the content of the ethylene unit is less than 1 mol%, the effect of improving the polarization performance and durability performance and the effect of reducing color spots in the resulting polarizing film are reduced, which is not preferable. On the other hand, if the ethylene unit content exceeds 4 mol%, the affinity of ethylene-modified PVA with water is lowered, the uniformity of the film film surface is lowered, and it is liable to cause color spots on the polarizing film. It is.

  Further, when copolymerizing ethylene and a vinyl ester monomer, if necessary, the copolymerizable monomer is within a range not impairing the effects of the invention (preferably 15 mol% or less, more preferably 5 mol% or less. Can also be copolymerized.

  Examples of monomers copolymerizable with such vinyl ester monomers include olefins having 3 to 30 carbon atoms such as propylene, 1-butene and isobutene; acrylic acid and salts thereof; methyl acrylate, ethyl acrylate, Acrylic acid esters such as n-propyl acrylate, i-propyl acrylate, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, octadecyl acrylate, etc. Methacrylic acid and salts thereof; methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, i-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, 2-methacrylic acid 2- Ethylhexyl, dodecyl methacrylate, methacrylate Methacrylic acid esters such as octadecyl acid; acrylamide, N-methylacrylamide, N-ethylacrylamide, N, N-dimethylacrylamide, diacetoneacrylamide, acrylamidepropanesulfonic acid and its salt, acrylamidopropyldimethylamine and its salt, N- Acrylamide derivatives such as methylolacrylamide and its derivatives; methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, methacrylamidepropanesulfonic acid and its salts, methacrylamidepropyldimethylamine and its salts, N-methylolmethacrylamide and its Methacrylamide derivatives such as derivatives; N-vinyl such as N-vinylformamide, N-vinylacetamide, N-vinylpyrrolidone Mido; Vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, n-butyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether, stearyl vinyl ether; acrylonitrile, methacrylonitrile, etc. Nitriles; vinyl halides such as vinyl chloride, vinylidene chloride, vinyl fluoride and vinylidene fluoride; allyl compounds such as allyl acetate and allyl chloride; maleic acid and its salts or esters; itaconic acid and its salts or its Esters; Vinylsilyl compounds such as vinyltrimethoxysilane; N-vinylamines such as isopropenyl acetate, N-vinylformamide, N-vinylacetamide, and N-vinylpyrrolidone Mention may be made of mids.

  The polymerization degree of the ethylene-modified PVA constituting the polarizer is 2000 to 4000, preferably 2200 to 3500, particularly preferably 2500 to 3000, from the viewpoint of polarization performance and durability. When the degree of polymerization of ethylene-modified PVA is less than 2000, the polarizing performance and durability performance of the polarizing film are lowered, which is not preferable. Moreover, when the polymerization degree is 4000 or less, it is preferable that the color spots of the polarizer hardly occur.

  The degree of polymerization of ethylene-modified PVA is the weight average degree of polymerization determined from GPC measurement. This weight average degree of polymerization is a value obtained by performing GPC measurement at 40 ° C. using hexafluoroisopropanol (HFIP) in which 20 mmol / liter sodium trifluoroacetate is added to the mobile phase using monodispersed PMMA as a standard. is there.

  The saponification degree of the ethylene-modified PVA constituting the polarizer is 99.0 to 99.99 mol% from the viewpoint of the polarization performance and durability of the polarizing film, more preferably 99.9 to 99.99 mol%, Particularly preferred is .95 to 99.99 mol%.

  As a method for producing an ethylene-modified PVA film, in addition to a film forming method by a melt extrusion method using ethylene-modified PVA containing water, for example, an ethylene-modified PVA solution in which ethylene-modified PVA is dissolved in a solvent is used for casting. A film forming method, a wet film forming method (discharge into a poor solvent), a gel film forming method (a method in which an ethylene-modified PVA aqueous solution is once cooled and gelated, and then the solvent is extracted and removed to obtain an ethylene-modified PVA film), and A method based on a combination of these can be employed. Among these, the casting film forming method and the melt extrusion film forming method are preferable from the viewpoint of obtaining a good ethylene-modified PVA film. The obtained ethylene-modified PVA film is subjected to drying and heat treatment as necessary.

  Examples of the solvent for dissolving the ethylene-modified PVA used in producing the ethylene-modified PVA film include dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylene glycol, glycerin, propylene glycol, diethylene glycol, and triethylene. Glycol, tetraethylene glycol, trimethylolpropane, ethylenediamine, diethylenetriamine, glycerin, water and the like can be mentioned, and one or more of these can be used. Among these, dimethyl sulfoxide, water, or a mixed solvent of glycerin and water is preferably used.

  The ratio of ethylene-modified PVA in the ethylene-modified PVA solution or water-containing ethylene-modified PVA used when producing an ethylene-modified PVA film varies depending on the degree of polymerization of ethylene-modified PVA, but is preferably 20 to 70% by mass. 25-60 mass% is more suitable, 30-55 mass% is still more suitable, and 35-50 mass% is the most suitable. If the proportion of ethylene-modified PVA exceeds 70% by mass, the viscosity of ethylene-modified PVA containing ethylene-modified PVA solution or water becomes too high, making filtration and defoaming difficult when preparing a stock solution of the film. It is difficult to obtain a film without any defects. On the other hand, when the proportion of the ethylene-modified PVA is lower than 20% by mass, the viscosity of the ethylene-modified PVA solution or the ethylene-modified PVA containing water becomes too low, and it becomes difficult to produce a PVA film having a target thickness. Further, this ethylene-modified PVA solution or ethylene-modified PVA containing water may contain a plasticizer, a surfactant, a dichroic dye, or the like, if necessary.

  When producing an ethylene-modified PVA film, it is preferable to add a polyhydric alcohol as a plasticizer. Examples of the polyhydric alcohol include ethylene glycol, glycerin, propylene glycol, diethylene glycol, diglycerin, triethylene glycol, tetraethylene glycol, trimethylolpropane, etc., and one or more of these are used. can do. Among these, diglycerin, ethylene glycol, and glycerin are preferably used because of the effect of improving stretchability.

  As addition amount of a polyhydric alcohol, 1-30 mass parts is preferable with respect to 100 mass parts of ethylene modified PVA, 3-25 mass parts is more preferable, 5-20 mass parts is the most preferable. When the amount is less than 1 part by mass, the dyeability and stretchability may be lowered. When the amount is more than 30 parts by mass, the ethylene-modified PVA film becomes too flexible and the handleability may be lowered.

  When producing an ethylene-modified PVA film, it is preferable to add a surfactant. The type of the surfactant is not particularly limited, but an anionic or nonionic surfactant is preferable. As the anionic surfactant, for example, a carboxylic acid type such as potassium laurate, a sulfate type such as octyl sulfate, and a sulfonic acid type anionic surfactant such as dodecylbenzenesulfonate are suitable. Nonionic surfactants include, for example, alkyl ether types such as polyoxyethylene oleyl ether, alkylphenyl ether types such as polyoxyethylene octylphenyl ether, alkyl ester types such as polyoxyethylene laurate, and polyoxyethylene laurylamino. Alkylamine type such as ether, alkylamide type such as polyoxyethylene lauric acid amide, polypropylene glycol ether type such as polyoxyethylene polyoxypropylene ether, alkanolamide type such as oleic acid diethanolamide, polyoxyalkylene allyl phenyl ether, etc. Nonionic surfactants such as allyl phenyl ether type are preferred. These surfactants can be used alone or in combination of two or more.

  As addition amount of surfactant, 0.01-1 mass part is preferable with respect to 100 mass parts of ethylene modified PVA, 0.02-0.5 mass part is more preferable, 0.05-0.3 mass part is Most preferred. If the amount is less than 0.01 parts by mass, the effect of improving the film forming property and the peelability is hardly exhibited, and if the amount is more than 1 part by mass, the surfactant elutes on the surface of the ethylene-modified PVA film and causes blocking. May decrease.

  The hot water cutting temperature of the ethylene-modified PVA film is preferably 66 to 73 ° C, more preferably 68 to 73 ° C, and even more preferably 70 to 73 ° C. When the hot water cutting temperature of the ethylene-modified PVA film is lower than 66 ° C., the melted film is stretched and molecular orientation hardly occurs, so that the polarizing performance of the polarizing film becomes insufficient. When the hot water cutting temperature is higher than 73 ° C., the film is not easily stretched, and the polarizing performance of the polarizing film is lowered, which is not preferable. When the ethylene-modified PVA film is subjected to drying and heat treatment, the hot water cutting temperature of the film can be adjusted by changing the temperature and time of the treatment.

  The ethylene-modified PVA film used for production of the polarizer preferably has a thickness of 10 to 50 μm, and more preferably 20 to 40 μm. If the thickness is less than 10 μm, the film strength is too low to perform uniform stretching, and color spots of the polarizing film are likely to occur. When the thickness exceeds 50 μm, when a polarizing film is prepared by uniaxially stretching an ethylene-modified PVA film, a thickness change due to neck-in at the end tends to occur, and color spots of the polarizing film are easily emphasized, which is not preferable.

  In order to produce a polarizing film from an ethylene-modified PVA film, for example, the ethylene-modified PVA film may be dyed, uniaxially stretched, fixed, and dried, and further subjected to heat treatment as necessary. There is no particular limitation on the order of operations of the fixed processing. Moreover, you may perform uniaxial stretching twice or more.

  Dyeing can be performed before uniaxial stretching, during uniaxial stretching, or after uniaxial stretching. As dyes used for dyeing, iodine-potassium iodide; direct black 17, 19, 154; direct brown 44, 106, 195, 210, 223; direct red 2, 23, 28, 31, 37, 39, 79, 81 240, 242, 247; Direct Blue 1, 15, 22, 78, 90, 98, 151, 168, 202, 236, 249, 270; Direct Violet 9, 12, 51, 98; Direct Green 1, 85; Direct Dichroic dyes such as yellow 8, 12, 44, 86, 87; direct orange 26, 39, 106, 107 can be used in one kind or a mixture of two or more kinds. Ordinary dyeing is generally performed by immersing the PVA film in a solution containing the above-mentioned dye, but the processing conditions and processing method are particularly limited, such as mixing with the PVA film to form a film. is not.

  For uniaxial stretching, wet stretching or dry heat stretching can be used, using warm water such as an aqueous boric acid solution (in a solution containing the dye or in a fixing treatment bath described later) or an ethylene-modified PVA film after water absorption. Can be done in air. The stretching temperature is not particularly limited, but is preferably 30 to 90 ° C. when the ethylene-modified PVA film is stretched (wet stretching) in warm water, and 50 to 180 ° C. is suitable for dry heat stretching. Further, the stretching ratio of uniaxial stretching (the total stretching ratio in the case of multi-stage uniaxial stretching) is preferably 4 times or more, and most preferably 5 times or more from the viewpoint of the polarizing performance of the polarizing film. The upper limit of the stretching ratio is not particularly limited, but it is preferably 8 times or less because uniform stretching is easily obtained. 2-20 micrometers is preferable and, as for the thickness of the film after extending | stretching, 5-15 micrometers is more preferable.

  Fixing treatment is often performed for the purpose of strengthening the adsorption of the dye to the ethylene-modified PVA film. Usually, boric acid and / or boron compounds are added to the treatment bath used for the fixing treatment. Moreover, you may add an iodine compound in a processing bath as needed.

  It is preferable to perform the drying process of the obtained polarizer at 30-150 degreeC, and it is more preferable to carry out at 50-150 degreeC.

  The polarizer obtained as described above uses the polarizing plate protective film of the present invention on one side, and uses another polarizing plate protective film even if the cellulose ester film of the present invention is used on the other side. May be.

  With respect to the cellulose ester film which is the polarizing plate protective film of the present invention, a commercially available cellulose ester film can be used as the polarizing plate protective film used on the other surface. For example, as a commercially available cellulose ester film, KC8UX2M, KC4UX, KC4FR, KC5UX, KC4UY, KC8UY, KC12UR, KC8UCR-3, KC8UCR-4, KC8UCR-5, KC8UY-HA, KC8UX-RHA )), Or a film such as a cyclic olefin resin other than a cellulose ester film, an acrylic resin, a polyester, or a polycarbonate.

  Generally, the polarizing plate protective film used for the surface corresponding to the outermost layer (viewing surface) of the liquid crystal display device preferably has a hard coat layer or an antiglare layer having a thickness of 8 to 20 μm. For example, a polarizing plate protective film having a hard coat layer or an antiglare layer described in JP-A Nos. 2003-114333, 2004-203309, 2004-354699, and 2004-354828 is preferably used. Furthermore, it is preferable to have an antireflection layer including at least a low refractive index layer on the hard coat layer or antiglare layer, and it is particularly preferable that the low refractive index layer contains hollow fine particles.

  The hollow fine particles referred to here are (1) composite particles composed of porous particles and a coating layer provided on the surface of the porous particles, or (2) hollow inside, and the content is a solvent, gas or Cavity particles filled with a porous material. In addition, the coating liquid for low refractive index layers should just contain either (1) composite particle | grains or (2) cavity particle | grains, and may contain both.

  The hollow particles are particles having cavities inside, and the cavities are surrounded by particle walls. The cavity is filled with contents such as a solvent, a gas, or a porous material used at the time of preparation. It is desirable that the average particle size of such inorganic fine particles is in the range of 5 to 300 nm, preferably 10 to 200 nm. The inorganic fine particles used are appropriately selected according to the thickness of the transparent film to be formed, and may be in the range of 2/3 to 1/10 of the film thickness of the formed transparent film such as a low refractive index layer. desirable. These inorganic fine particles are preferably used in a state of being dispersed in an appropriate medium in order to form a low refractive index layer. As the dispersion medium, water, alcohol (for example, methanol, ethanol, isopropyl alcohol), ketone (for example, methyl ethyl ketone, methyl isobutyl ketone), and ketone alcohol (for example, diacetone alcohol) are preferable.

  The thickness of the coating layer of the composite particles or the thickness of the particle walls of the hollow particles is desirably in the range of 1 to 20 nm, preferably 2 to 15 nm. In the case of composite particles, when the thickness of the coating layer is less than 1 nm, the particles may not be completely covered, and the low refractive index effect may not be sufficiently obtained. On the other hand, when the thickness of the coating layer exceeds 20 nm, the porosity (pore volume) of the composite particles may be lowered, and the low refractive index effect may not be sufficiently obtained. In the case of hollow particles, if the particle wall thickness is less than 1 nm, the particle shape may not be maintained, and even if the thickness exceeds 20 nm, the effect of low refractive index may not be sufficiently exhibited. is there.

The coating layer of the composite particle or the particle wall of the hollow particle contains silica as a main component. The coating layer of the composite particle or the particle wall of the hollow particle may contain a component other than silica, specifically, Al ₂ O ₃ , B ₂ O ₃ , TiO ₂ , ZrO ₂ , SnO _{2. , CeO 2, P 2 O 3} , Sb 2 O 3, Mo
Examples thereof include O ₃ , ZnO ₂ , and WO ₃ . Examples of the porous particles constituting the composite particles include those made of silica, those made of silica and an inorganic compound other than silica, and those made of CaF ₂ , NaF, NaAlF ₆ , MgF, and the like. Among these, porous particles made of a composite oxide of silica and an inorganic compound other than silica are particularly preferable. Examples of inorganic compounds other than silica include Al ₂ O ₃ , B ₂ O ₃ , TiO ₂ , ZrO ₂ , SnO ₂ , CeO ₂ , P ₂ O ₃ , Sb ₂ O ₃ , MoO ₃ , ZnO ₂ , WO _{3 and the} like. 1 type or 2 types or more can be mentioned. In such porous particles, the molar ratio MOX / SiO ₂ when the silica is represented by SiO ₂ and the inorganic compound other than silica is represented by oxide (MOX) is 0.0001 to 1.0, preferably It is desirable to be in the range of 0.001 to 0.3. It is difficult to obtain a porous particle having a molar ratio MOX / SiO ₂ of less than 0.0001, and even if it is obtained, conductivity is not exhibited. On the other hand, if the molar ratio MOX / SiO _{2 of} the porous particles exceeds 1.0, the ratio of silica decreases, so that particles having a small pore volume and a low refractive index may not be obtained.

  The pore volume of such porous particles is desirably in the range of 0.1 to 1.5 ml / g, preferably 0.2 to 1.5 ml / g. If the pore volume is less than 0.1 ml / g, particles having a sufficiently reduced refractive index cannot be obtained. If the pore volume exceeds 1.5 ml / g, the strength of the fine particles is lowered, and the strength of the resulting coating may be lowered. is there.

  Incidentally, the pore volume of such porous particles can be determined by a mercury intrusion method. Examples of the contents of the hollow particles include a solvent, a gas, and a porous substance used at the time of preparing the particles. The solvent may contain an unreacted particle precursor used when preparing the hollow particles, the catalyst used, and the like. Moreover, what consists of the compound illustrated by the said porous particle as a porous substance is mentioned. These contents may be composed of a single component or may be a mixture of a plurality of components.

  As a method for producing such inorganic fine particles, for example, the method for preparing composite oxide colloidal particles disclosed in paragraphs [0010] to [0033] of JP-A-7-133105 is suitably employed. Specifically, when the composite particles are composed of silica and an inorganic compound other than silica, the inorganic compound particles are produced from the following first to third steps.

First Step: Preparation of Porous Particle Precursor In the first step, an alkali aqueous solution of a silica raw material and an inorganic compound raw material other than silica is separately prepared in advance, or a silica raw material and an inorganic compound raw material other than silica are prepared in advance. A mixed aqueous solution is prepared, and this aqueous solution is gradually added to an aqueous alkaline solution having a pH of 10 or more while stirring according to the composite ratio of the target composite oxide to prepare a porous particle precursor.

  As the silica raw material, alkali metal, ammonium or organic base silicate is used. Sodium silicate (water glass) or potassium silicate is used as the alkali metal silicate. Examples of the organic base include quaternary ammonium salts such as tetraethylammonium salt, and amines such as monoethanolamine, diethanolamine, and triethanolamine. The ammonium silicate or the organic base silicate includes an alkaline solution obtained by adding ammonia, a quaternary ammonium hydroxide, an amine compound or the like to a silicic acid solution.

  Alternatively, it is also preferable to use a polarizing plate protective film that also serves as an optical compensation film having an optical anisotropic layer formed by aligning liquid crystal compounds such as discotic liquid crystal, rod-shaped liquid crystal, and cholesteric liquid crystal. For example, the optically anisotropic layer can be formed by the method described in JP-A-2003-98348.

  The polarizing plate of the present invention can be further constructed by laminating a protective film on one surface of the polarizing plate and a separate film on the other surface. The protective film and the separate film are used for the purpose of protecting the polarizing plate at the time of shipping the polarizing plate and at the time of product inspection. In this case, the protect film is bonded for the purpose of protecting the surface of the polarizing plate, and is used on the side opposite to the surface where the polarizing plate is bonded to the liquid crystal plate. Moreover, a separate film is used in order to cover the contact bonding layer bonded to a liquid crystal board, and is used for the surface side which bonds a polarizing plate to a liquid crystal cell.

  The polarizing plate of the present invention has a thickness of 80 with a polarizing plate protective film A having a thickness of 30 to 60 μm and a polarizing plate protective film B also serving as a retardation plate having a thickness of 30 to 60 μm sandwiching a polarizer. It is a ~ 160-micrometer polarizing plate, It is preferable that the stiffness (ST) in 23 degreeC and 55% RH of this polarizing plate is the range of 20-80 (g).

  The method for measuring the stiffness of the polarizing plate at 23 ° C. and 55% RH is as follows.

<Measurement of stiffness>
A polarizing plate is cut into a dimension of 35 mm in width and 105 mm in length, and both ends are fixed with double-sided tape having a width of 5 mm, and a ring is formed at a portion of the film having a length of 100 mm. The part where both ends were stuck together was fixed to the base, and pushed vertically from the top of the ring, and the load (g) when the ring was pushed 10 mm was read with a load cell to obtain stiffness. At this time, the measurement environment was maintained at 23 ° C. and 55% RH.

(Liquid crystal display device)
By incorporating the polarizing plate of the present invention into a commercially available VA mode, IPS (In Plane Switching) mode type liquid crystal display device, the liquid crystal display device of the present invention having excellent visibility and an increased viewing angle can be produced. . In the present invention, the transverse electric field switching mode includes a fringe field switching (FFS) mode, and the polarizing plate of the present invention can be incorporated in the same manner as the IPS mode, and the liquid crystal of the present invention having the same effect. A display device can be manufactured.

  When the polarizing plate protective film of the present invention is installed in a liquid crystal display device, the polarizing plate protective film having a hard coat layer of the present invention is positioned on the backlight side between the driving liquid crystal cell and the backlight. Placed in. The effect of the present invention is exhibited by this arrangement, and when a brightness enhancement film using polarized light is used between the polarizing plate protective film of the present invention and the backlight, the present invention exhibits the maximum effect. To do. Examples of the brightness enhancement film include DBEF (brightness enhancement film manufactured by Sumitomo 3M Limited).

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.
(Synthesis of polymers X and Y)
Bulk polymerization was performed by the polymerization method described in JP-A No. 2000-344823. That is, the contents were heated to 70 ° C. while introducing the following methyl methacrylate and ruthenocene into a flask equipped with a stirrer, a nitrogen gas inlet tube, a thermometer, an inlet, and a reflux condenser. Next, half of the following β-mercaptopropionic acid which had been sufficiently purged with nitrogen gas was added to the flask under stirring. After the addition of β-mercaptopropionic acid, the contents in the stirring flask were maintained at 70 ° C. and polymerization was carried out for 2 hours. Further, after adding the other half of β-mercaptopropionic acid substituted with nitrogen gas, the temperature of the content being stirred was maintained at 70 ° C., and polymerization was carried out for 4 hours. The temperature of the reaction product was returned to room temperature, and 20 parts by mass of a 5% by mass benzoquinone tetrahydrofuran solution was added to the reaction product to stop the polymerization. While gradually heating the polymer to 80 ° C. under reduced pressure with an evaporator, tetrahydrofuran, residual monomer and residual thiol compound were removed to obtain polymer AC11. The weight average molecular weight was 1000.
Methyl methacrylate 100 parts by mass Ruthenocene (metal catalyst) 0.05 parts by mass β-mercaptopropionic acid 12 parts by mass In addition, the amount of reaction stopper and the timing of addition were adjusted to obtain AC9 to 10 and 12 to 13. Furthermore, polymers AC1 to 8 were synthesized with reference to the method described in JP2003-12859A. The prepared samples are shown in Tables 1 and 2.

(Polyester polymerization)
A three-necked flask is equipped with a stirrer, nitrogen gas inlet tube, thermometer, and water removal tube. The dewatering pipe has a fractionation pipe, a top thermometer and a cooling pipe at the tip, and a water receiver with a scale (ml) under the cooling pipe, and the receiver has an exhaust pipe at the top. Yes. Put 186 g of ethylene glycol and 236 g of succinic acid in the flask, warm the internal temperature to 80-90 ° C. while slowly flowing nitrogen gas, and start stirring. The temperature is raised to 150-160 ° C. over 1 hour. At this time, the top temperature does not exceed 100 ° C. (only water is distilled out of the system so that glycol does not accumulate), the water is discharged, and the temperature is set to 190 to 200 ° C. When 72 g is distilled, the internal temperature is lowered to 110 to 120 ° C., 120 g of acetic acid is added, and the temperature is again raised to 150 to 160 ° C. When 36 g of water was further distilled, the internal temperature was lowered to 110 to 120 ° C. and further lowered to 80 ° C. Thereafter, it was precipitated with acetone, and the precipitate was collected by filtration to obtain K1. As a result of measuring the molecular weight of K1 by GPC, the weight average molecular weight was 434.
(Polymerization of K2-11)
In the same manner as for K1, divalent alcohols and divalent carboxylic acids as shown in Tables 3 and 4 are combined and heated, and stirred. When water is distilled, the internal temperature is lowered, and the monoalcohol or monocarboxylic acid shown in Tables 3 and 4 is added, and the temperature is increased again and stirred. Further, when water was distilled off, the internal temperature was lowered and the mixture was precipitated with acetone, and the precipitate was collected by filtration to obtain K2-11. The molecular weight was adjusted by changing the amount of distilled water. Regarding K5 and K7, the mixing ratio of the two types of alcohol and carboxylic acid was 1: 1. The weight average molecular weight of the obtained polymer was as follows. The numerical values in parentheses below are weight average molecular weights. K2 (800), K3 (234), K4 (3000), K5 (6000), K6 (10000), K7 (11000), K8 (234), K9 (1000), K10 (8000), K11 (10000). The prepared samples are shown in Tables 3 and 4.

(Preparation of cellulose ester film S1)
<Dope composition>
Cellulose triacetate (acetylation degree 61.5%) 100 parts by mass 2- (2′-hydroxy-3 ′, 5′-di-t-butylphenyl) benzotriazole
2 parts by mass AC1 (Polymer X) 30 parts by mass Methylene chloride 475 parts by mass Ethanol 50 parts by mass The dope composition is put into a sealed container, heated to 70 ° C., and stirred to completely dissolve cellulose triacetate (TAC). A dope was obtained. The time required for dissolution was 4 hours. After the dope composition was filtered, it was uniformly cast on a stainless band support having a dope temperature of 35 ° C. and a temperature of 22 ° C. using a belt casting apparatus. The temperature of the stainless steel band support was 20 ° C.

Then, after making it dry to the range which can be peeled, dope was peeled from the stainless steel band support body. At this time, the residual solvent amount of the dope was 25%. The time required from casting the dope to peeling was 3 minutes. After peeling from the stainless steel band support, it was dried at 120 ° C. while being stretched 1.01 times in the width direction with a tenter, and then released at 120 ° C. while being released in width and conveyed by a number of rolls. Thereafter, drying was further terminated in a drying zone at 135 ° C., and knurling with a width of 10 mm and a height of 5 μm was applied to both ends of the film to produce a cellulose ester film S1 having a thickness of 40 μm. The film width was 1300 mm and the winding length was 3000 m. The winding tension was an initial tension of 150 N / 1300 mm and a final winding tension of 100 N / 1300 mm.
(Production of cellulose ester films S2 to S35)
In the production of the cellulose ester film S1, AC1 is replaced with the polymer X shown in Table 5 and the addition amount thereof, and polymer Y and polyester are added to some films, and the film thicknesses are shown in Tables 5 and 6 below. Cellulose ester films S2 to S35 were prepared as described.

<Preparation of cellulose ester film having hard coat layer and back coat layer>
On the cellulose ester films S1 to 15 and S18 to 31, the following hard coat layer coating solution is filtered through a polypropylene filter having a pore size of 0.4 μm to prepare a hard coat layer coating solution, which is then used with a micro gravure coater. After coating at 90 ° C. and drying at 90 ° C., a hard coat layer having a dry film thickness of 10 μm is cured by using an ultraviolet lamp to cure the coating layer with an illumination intensity of 100 mW / cm ² and an irradiation dose of 0.1 J / cm ^2. To form a hard coat film.
(Hard coat layer coating solution)
The following materials were stirred and mixed to obtain a hard coat layer coating solution.
Acrylic monomer: KAYARAD DPHA (dipentaerythritol hexaacrylate, Nippon Kayaku) 220 parts by mass Irgacure 184 (manufactured by Ciba Specialty Chemicals) 20 parts by mass Propylene glycol monomethyl ether 110 parts by mass Ethyl acetate 110 parts by mass The coating layer composition was applied by an extrusion coater so as to have a wet film thickness of 10 μm, dried at 85 ° C. and wound up to provide a backcoat layer.
(Backcoat layer composition)
Acetone 54 parts by weight Methyl ethyl ketone 24 parts by weight Methanol 22 parts by weight Diacetylcellulose 0.6 part by weight Ultrafine silica 2% acetone dispersion (Aerosil 200V manufactured by Nippon Aerosil Co., Ltd.) Cellulose ester after 0.2 parts by weight or more Hard coat films H1 to 15 and H18 to 31 on which a hard coat layer of the film was applied were obtained.

  Furthermore, the following antireflection layer was coated on H18.

<Coating of antireflection layer>
On the hard coat film H18 produced above, an antireflection layer was applied in the order of a high refractive index layer and then a low refractive index layer as described below to produce an antireflection film.

(High refractive index layer)
On the hard coat film, the following high refractive index layer coating composition was applied with an extrusion coater, dried at 80 ° C. for 1 minute, then cured by irradiation with ultraviolet rays of 0.1 J / cm ² , and further at 100 ° C. for 1 minute. A high refractive index layer was provided so as to have a thickness of 78 nm by thermosetting.
The refractive index of this high refractive index layer was 1.62.

(High refractive index layer coating composition)
Isopropyl alcohol solution of metal oxide fine particles (solid content 20%, ITO particles, particle size 5 nm) 55 parts by mass Metal compound: Ti (OBu) ₄ (tetra-n-butoxytitanium) 1.3 parts by mass Ionizing radiation curable resin : Dipentaerythritol hexaacrylate
3.2 parts by mass Photopolymerization initiator: Irgacure 184 (manufactured by Ciba Specialty Chemicals)
0.8 parts by mass 10% propylene glycol monomethyl ether solution of linear dimethyl silicone-EO block copolymer (FZ-2207, manufactured by Nippon Unicar Co., Ltd.) 1.5 parts by mass Propylene glycol monomethyl ether 120 parts by mass Isopropyl alcohol 240 parts by mass Methyl ethyl ketone 40 parts by mass (low refractive index layer)
On the high refractive index layer, the following low refractive index layer coating composition was applied with an extrusion coater, dried at 100 ° C. for 1 minute, cured by irradiation with ultraviolet rays of 0.1 J / cm ² , and further 120 An antireflection film was prepared by thermosetting at 5 ° C. for 5 minutes and providing a low refractive index layer so as to have a thickness of 95 nm. The refractive index of this low refractive index layer was 1.37.

(Preparation of low refractive index layer coating composition)
<Preparation of tetraethoxysilane hydrolyzate A>
Hydrolyzate A was prepared by mixing 289 g of tetraethoxysilane and 553 g of ethanol, adding 157 g of 0.15% aqueous acetic acid solution thereto, and stirring in a water bath at 25 ° C. for 30 hours.
Tetraethoxysilane hydrolyzate A 110 parts by mass hollow silica fine particles (P-2 below) 30 parts by mass KBM503 (silane coupling agent, manufactured by Shin-Etsu Chemical Co., Ltd.) 4 parts by mass linear dimethylsilicone-EO block copolymer (FZ) -2207, manufactured by Nihon Unicar Co., Ltd.) 10% propylene glycol monomethyl ether solution 3 parts by mass Propylene glycol monomethyl ether 400 parts by mass Isopropyl alcohol 400 parts by mass <Preparation of hollow silica-based fine particles P-2>
A mixture of 100 g of silica sol having an average particle diameter of 5 nm and a SiO ₂ concentration of 20% by mass and 1900 g of pure water was heated to 80 ° C. The pH of this reaction mother liquor was 10.5, and 9000 g of 0.98 mass% sodium silicate aqueous solution as SiO ₂ and 9000 g of 1.02 mass% sodium aluminate aqueous solution as Al ₂ O ₃ were simultaneously added to the mother liquor. did. Meanwhile, the temperature of the reaction solution was kept at 80 ° C. The pH of the reaction solution rose to 12.5 immediately after the addition and hardly changed thereafter. After completion of the addition, the reaction solution was cooled to room temperature and washed with an ultrafiltration membrane to prepare a SiO ₂ .Al ₂ O ₃ core particle dispersion with a solid content concentration of 20% by mass (step (a)).

1700 g of pure water is added to 500 g of this core particle dispersion and heated to 98 ° C., and while maintaining this temperature, a silicic acid solution (SiO ₂₎ obtained by dealkalizing a sodium silicate aqueous solution with a cation exchange resin. A dispersion of core particles in which a first silica coating layer was formed by adding 3000 g (concentration: 3.5% by mass) was obtained (step (b)).

Next, 1125 g of pure water is added to 500 g of the core particle dispersion liquid that has been washed with an ultrafiltration membrane to form a first silica coating layer having a solid concentration of 13% by mass, and concentrated hydrochloric acid (35.5%) is further added dropwise. The pH was adjusted to 1.0 and dealumination was performed. Next, the aluminum salt dissolved in the ultrafiltration membrane was separated while adding 10 L of hydrochloric acid aqueous solution of pH 3 and 5 L of pure water, and SiO ₂ · Al from which some of the constituent components of the core particles forming the first silica coating layer were removed. A dispersion of ₂ O ₃ porous particles was prepared (step (c)).

A mixture of 1500 g of the above porous particle dispersion, 500 g of pure water, 1.750 g of ethanol and 626 g of 28% ammonia water is heated to 35 ° C., and then 104 g of ethyl silicate (SiO ₂ 28 mass%) is added. The surface of the porous particles on which the first silica coating layer was formed was coated with a hydrolyzed polycondensate of ethyl silicate to form a second silica coating layer. Subsequently, a dispersion of hollow silica-based fine particles (P-2) having a solid content concentration of 20% by mass in which the solvent was replaced with ethanol using an ultrafiltration membrane was prepared.

The thickness of the first silica coating layer of the hollow silica-based fine particles was 3 nm, the average particle size was 47 nm, MO _x / SiO ₂ (molar ratio) was 0.0017, and the refractive index was 1.28. Here, the average particle diameter was measured by a dynamic light scattering method.

(Heat treatment)
The produced film coated with the antireflection layer was subjected to heat treatment at 80 ° C. for 4 days in a heat treatment chamber to obtain H18 coated with the antireflection layer.

In addition, a hard coat layer having the following AG function was applied to the cellulose ester films S16 and 17 instead of the hard coat layer.
<Production of hard coat film having AG function>
As transparent resin, 100 parts of zirconium-containing UV acrylate resin with a refractive index of 1.67 (trade name: KZ7391, solid content concentration 42%, manufactured by JSR) and 18 parts of dipentaerythritol hexaacrylate with a refractive index of 1.51 are mixed. A transparent resin solution having a refractive index at curing of 1.60 and a solid content concentration of 51% was obtained. 100 parts of this transparent resin solution, 1 part of 2-hydroxy-2-methylpropiophenone as a photoinitiator, and resin resin fine particles made of silicone resin having a refractive index of 1.42 and an average particle size of 2.4 μm ( 3.6 parts of a height of 1.7 μm, a diameter of 1.8 μm, a thickness of 0.35 μm), 5.4 parts of spherical resin fine particles made of silicone resin having a refractive index of 1.42 and an average particle diameter of 2.4 μm, and methyl as a solvent A coating material was obtained by adding 41 parts of isobutyl ketone and dispersing in a sand mill for 30 minutes. The obtained paint was applied on a transparent substrate made of TAC having a film thickness of 80 μm and transmittance of 94% by a reverse coating method, dried at 100 ° C. for 2 minutes, and then one 120 W / cm condensing type high-pressure mercury lamp. Were irradiated with ultraviolet rays (irradiation distance 10 cm, irradiation time 30 seconds), and the coating film was cured to produce hard coat films H16 and 17 having an AG function having an antiglare layer having a thickness of 1.8 μm.
[Evaluation]
The following evaluation was performed on the obtained cellulose ester films S1 to S35, and the results are shown in Tables 5 and 6.
(Flatness)
Cut each sample into a size of 90cm in width and 100cm in length, and arrange five 50W fluorescent lamps at a height of 1.5m so that the sample stage can be illuminated from a 45 ° angle. Each film sample was placed, and the unevenness that appeared to be reflected on the film surface was visually observed and judged as follows. By this method, it is possible to determine “tsun”, “wrinkle”, and “curl”.

◎: All five fluorescent lamps look straight ○: Some fluorescent lamps appear to be bent slightly △: Fluorescent lamps appear to be slightly bent overall ×: Fluorescent lamps appear to swell greatly (measurement of Ro and Rt) )
The average refractive index of the cellulose ester film was measured using an Abbe refractometer (4T). Moreover, the thickness of the film was measured using a commercially available micrometer.

  Using an automatic birefringence meter KOBRA-21ADH (manufactured by Oji Scientific Instruments), film retardation measurement at a wavelength of 590 nm was performed under the same environment for 24 hours in an environment of 23 ° C. and 55% RH. went. The above-mentioned average refractive index and film thickness were input into the following formula, and values of in-plane retardation (Ro) and retardation in the thickness direction (Rt) were obtained.

Formula (i) Ro = (nx−ny) × d
Formula (II) Rt = {(nx + ny) / 2−nz} × d
(Here, the refractive index in the slow axis direction in the plane of the cellulose ester film is nx, the refractive index in the direction perpendicular to the slow axis in the plane is ny, the refractive index in the thickness direction of the film is nz, d is Represents the thickness (nm) of the film.)
(Rt stability)
The cellulose ester film thus prepared was treated at 23 ° C. and 80% RH for 10 hours, and then Rt was measured. Further, this film was treated at 23 ° C. and 20% RH for 10 hours, and Rt was measured. evaluated.

ΔRt (nm) = Rt (23 ° C., 80% RH) −Rt (23 ° C., 20% RH)
A: ΔRt is less than 10 nm B: ΔRt is less than 10-15 nm Δ: ΔRt is less than 15-20 nm X: ΔRt is 20 nm or more (dimensional stability)
The prepared cellulose ester film was treated at 80 ° C. and 90% RH for 120 hours with two marks (crosses) in the film transport direction (MD direction) and the direction perpendicular to the film direction (TD direction), and before the treatment. The distance of the mark (cross) after the treatment was measured with an optical microscope, and evaluated according to the following criteria.

Dimensional change rate (%) = [(a1-a2) / a1] × 100
a1: Distance before heat treatment a2: Distance after heat treatment A: Dimensional change rate of less than 0.1% B: Dimensional change rate of 0.1% to less than 0.5% C: Dimensional change rate of 0.5% to Less than 1.0% D: The dimensional change rate is 1.0% to less than 1.5% E: The dimensional change rate is 1.5% to less than 2.0% F: The dimensional change rate is 2.0% to 3. Less than 0% G: Dimensional change rate is 3.0% to 5.0% or more From the above table, the cellulose ester film of the present invention is superior in comparison with flatness, Rt stability, and dimensional stability. I understand.
(Preparation of polarizing plates 1-31)
The cellulose ester films H1 to H31 were alkali-treated with a 2.5 mol / L sodium hydroxide aqueous solution at 40 ° C. for 60 seconds, washed with water for 3 minutes to form a saponified layer, and an alkali-treated film was obtained. Next, this film is bonded to one side of a polarizer with a 5% aqueous solution of completely saponified polyvinyl alcohol as an adhesive, and KC4UY (Konica Minolta Opto Co., Ltd.) is bonded to the other side and dried. 1 to 11 and 16 to 31 were produced.

In addition, KC4FR (manufactured by Konica Minolta Opto Co., Ltd.) and S14 which is the polarizing plate of the present invention were bonded in place of KC4UY, and polarizing plates 12, 13, 14 and 15 were produced, respectively. (Preparation of polarizing plates 32 to 38)
With the combination of cellulose ester films shown in Table 7, a film was bonded to a polarizer in the same manner as in the production of the polarizing plates 1 to 31 to produce polarizing plates 32 to 38. Note that one side of the polarizing plate 36 is KC8UX-HA (Ro: 1.0 nm, Rt: 48 nm, manufactured by Konica Minolta Opto), 37 is KC8UX-H (Ro: 1.2 nm, Rt: 49 nm, KC8UY-HA (Ro: 1.0 nm, Rt: 55 nm, manufactured by Konica Minolta Opto) was used for 38.

  The following evaluation was performed about the obtained polarizing plates 1-38.

(Polarizing plate degradation)
The produced polarizing plate was treated at 80 ° C. and 90% RH for 120 hours, the transmittance before and after the treatment was measured, and evaluated according to the following criteria in five stages.

Difference in transmittance ΔT (%) = Td (transmittance after high temperature and high humidity treatment) −T0 (transmittance before high temperature and high humidity treatment)
◎: ΔT is less than 1% ○: ΔT is less than 1% to less than 5% △: ΔT is less than 5% to less than 10% ×: ΔT is less than 10% to less than 15% XX: ΔT is more than 15% )
The prepared polarizing plate was marked with two marks (crosses) in the direction of the absorption axis of the polarizer and treated at 80 ° C. and 90% RH for 120 hours, and the distance between the mark (cross) before and after the treatment was optically measured. Measured with a microscope and evaluated in five stages according to the following criteria.

Dimensional change rate (%) = [(a1-a2) / a1] × 100
a1: Distance before heat treatment a2: Distance after heat treatment A: Dimensional change rate of less than 0.1% B: Dimensional change rate of 0.1% to less than 0.5% C: Dimensional change rate of 0.5% to Less than 1.0% D: The dimensional change rate is 1.0% to less than 1.5% E: The dimensional change rate is 1.5% to less than 2.0% F: The dimensional change rate is 2.0% to 3. Less than 0% G: Dimensional change rate is 3.0% to 5.0% or more (viewing angle fluctuation)
<Production of liquid crystal display device>
A liquid crystal panel for viewing angle measurement was produced as follows, and the characteristics as a liquid crystal display device were evaluated.

  Only the polarizing plate on the back side (backlight side) of Hitachi 32-inch display W32-L7000, which was previously bonded, is peeled off, and the prepared polarizing plates 1 to 38 are respectively placed on the glass of the liquid crystal cell so as to be on the backlight side. Pasted. At that time, the direction of bonding of the polarizing plates was performed such that the absorption axis was directed in the same direction as the polarizing plates bonded in advance, and liquid crystal display devices 1 to 38 were produced.

  In addition, about the polarizing plates 14, 15, and 35, as shown in Table 7, it bonded so that the cellulose-ester film S14 of this invention might match | combine with a glass cell.

  The following evaluation was performed using the liquid crystal display devices 1 to 38 produced as described above.

  The viewing angle of the liquid crystal display device was measured using EZ-Contrast 160D manufactured by ELDIM in an environment of 23 ° C. and 55% RH. Subsequently, the polarizing plate was treated at 60 ° C. and 90% RH for 500 hours, and the measurement was performed in the same manner. Furthermore, what processed the said polarizing plate at 60 degreeC and 90% RH for 1000 hours was measured similarly, and three steps evaluation was carried out with the following reference | standard.

◎: No viewing angle variation △: Viewing angle variation is recognized ×: Viewing angle variation is very large (CM (corner unevenness))
Similarly to the viewing angle evaluation described above, a polarizing plate was attached to prepare liquid crystal display devices 1 to 38. These liquid crystal display devices 1 to 38 were treated at 60 ° C. for 300 hours and then returned to 23 ° C. and 55% RH. Then, after turning on the power and turning on the backlight, light leakage of black display after 2 hours was visually observed and evaluated according to the following criteria.

A: There is no light leakage. O: There are 1 to 2 weak light leaks. Δ: There are 1 to 2 strong light leaks. X: There are 3 or more strong light leaks.

  From the above table, it can be seen that the polarizing plate and the liquid crystal display device using the polarizing plate protective film of the present invention are superior in comparison with polarizing plate deterioration, dimensional change, corner unevenness, and viewing angle fluctuation.

Claims (6)

In two polarizing plate protective films sandwiching a polarizer for forming a polarizing plate, at least one of the two polarizing plate protective films has an Ro defined by the following formula (I) of 0 to 10 nm, Rt defined by the following formula (II) is -20 to 20 nm and has a hard coat layer, and at least an ethylenically unsaturated monomer Xa having no aromatic ring and no hydrophilic group in the molecule; Polymer X having a weight average molecular weight of 5,000 to 30,000 obtained by copolymerization with ethylenically unsaturated monomer Xb having no aromatic ring and having a hydrophilic group, and ethylenically unsaturated monomer Ya having no aromatic ring A cellulose ester containing either a polymer Y having a weight average molecular weight of 500 or more and 3000 or less obtained by polymerization of Polarizing plate protective film, which is a ether film.
Formula (I) Ro = (nx−ny) × d
Formula (II) Rt = {(nx + ny) / 2−nz} × d
(Here, the refractive index in the slow axis direction in the plane of the polarizing plate protective film is nx, the refractive index in the direction perpendicular to the slow axis in the plane is ny, and the refractive index in the thickness direction of the film is nz, d. Represents the thickness (nm) of the film.)
Formula _{(3) B 1 - (G} -A-) wG-B 1
(In the formula, B ₁ represents a monocarboxylic acid, G represents a divalent alcohol, A represents a dibasic acid, and B ₁ , G, and A do not contain an aromatic ring. W represents the number of repetitions. A plurality of B ₁ and G may be the same or different.)
Formula _{(4) B 2 - (A} -G-) zA-B 2
(In the formula, B ₂ represents a monoalcohol, G represents a divalent alcohol, and A represents a dibasic acid.
The B ₂ , G and A do not contain an aromatic ring. z represents the number of repetitions. A plurality of B ₂ and G may be the same or different. ) The said polymer X is shown by the following general formula (1), and the said polymer Y is shown by the following general formula (2), The polarizing plate protective film of Claim 1 characterized by the above-mentioned.
General formula (1)
  -[CH ₂ -C (-R ₁ ) (-CO ₂ R ₂ )] M- [CH ₂ -C (-R ₃ ) (-CO ₂ R ₄ -OH)-] n- [Xc] p-
  General formula (2)
  Ry- [CH ₂ -C (-R ₅ ) (-CO ₂ R ₆ -OH)-] k- [Yb] q-
(Wherein R ₁ , R ₃ , R ₅ Is H or CH ₃ Represents. R ₂ Represents an alkyl group having 1 to 12 carbon atoms or a cycloalkyl group. R ₄ , R ₆ Is -CH ₂ -, -C ₂ H ₄ -Or-C ₃ H ₆ -Represents.
Ry represents OH, H or an alkyl group having 3 or less carbon atoms. Xc represents a monomer unit that can be polymerized to Xa and Xb. Yb represents a monomer unit copolymerizable with Ya. m, n, k, p, and q represent a molar composition ratio. However, m ≠ 0, n ≠ 0, k ≠ 0, m + n + p = 100, and k + q = 100. ) When the cellulose ester film contains a polymer X and a polymer Y, the content thereof is in a range satisfying the following formula (i) and formula (ii). Polarizing plate protective film.
Formula (i) 5 ≦ Xg + Yg ≦ 35 (mass%)
Formula (ii) 0.05 ≦ Yg / (Xg + Yg) ≦ 0.4
(In the formula, Xg represents the content (mass%) of polymer X relative to the cellulose ester, and Yg represents the content (mass%) of polymer Y relative to the cellulose ester.) The thickness of the said hard-coat layer is 1-30 micrometers in thickness, The polarizing plate protective film as described in any one of Claim 1- Claim 3 characterized by the above-mentioned. A polarizing plate comprising the polarizing plate protective film according to claim 4 bonded to at least one surface of a polarizer. A liquid crystal display device using the polarizing plate according to claim 5.